3GP DVR Spy Pen Review

There may be a good reason why the most recent Bond films lack the abundance of cool gadgets we got used to from the older movies. As with watch phones (see the Nova N800 review), other gizmos that were considered strictly-movie-territory are now coming within the reach of the average person. It may prove too difficult finding new gadgets that are still plausible enough not to shatter the suspension of disbelief of moviegoers. Maybe that's why the makers of the Bond films chose to drop the gadgets instead of “nuking the fridge”.

Like I said in my other review, I'm a sucker for gadgets. If something with a certain degree of coolness catches my eye, it's nearly impossible to resist buying it (this must be like the women & shoes thing). One of those gizmos that could come straight out of an older Bond movie is a pen with a pretty decent video and still photo camera built-in, in other words a ‘DVR spy pen’. Here's a review.

One Pen to rule them all

I start out with a word of caution. If you intend to buy a gadget pen like this, don't just buy the first thing that you can find. You may be in for a disappointment. There are probably 10+ different models, and although they all look very similar, they perform in a wide range between pathetically and pretty well. This became apparent when I skimmed through eBay and other websites. The price of the pens varies mostly with their quality, but some people sell the most crappy model for a price that buys two of the best pens elsewhere.

So after my usual comparison of all models I could find, I settled for one particular pen, which is known under the name “M-909” or the “3GP spy pen”. This one stands out from most of the rest by three features:

  1. direct recording to 3GP format with MPEG-4 video compression,
  2. the ability to take still photos next to videos, and
  3. 640×480 video resolution at a maximal 30 frames per second and a whopping 2048×1536 photo resolution.

The good news is, the MPEG-4 compression offers a combination of very good picture quality and small file size. You'll be able to record hours and hours of video before the 4GB of storage runs out. Most of the other pens only record video at 320×240 using the much less efficient MJPEG codec, and take still photos — if at all — at 640×480 or maybe 1280×960.
Now the bad news, this particular pen is very hard to find (and there's some more bad news further on). There's a company in the USA, EyeSpyPro, which sells the M-909, but the price is somewhat steep, especially for overseas customers who will get extra customs taxes on top. (Note from the year 2020: this company seems gone now, their website used to be eyespypro.com.) They do offer a good service and warranty though, you are guaranteed to get the correct pen, and you get some extras, so it's worth considering. I however, wanted to strike a balance between my craving for gadgets and my budget, so I skimmed through eBay and found exactly one Hong Kong seller who sold exactly one of these pens. I paid about $70, i.e. €53. Search for “3gp spy pen” in eBay and you might find the same pen if he sells more of them.

The package arrived pretty quickly for Hong Kong-to-Belgium shipping, and the box looked identical to the one sold at EyeSpyPro, so it's definitely the same pen (even more proof follows). The contents of the box are:

  • The pen itself
  • A USB extension cord
  • A USB wall charger with USA prongs (identical to the one supplied with the Nova N800)
  • A small CD (not suitable for slot-loading drives) with a manual and instructions.

On the pen itself was a program with a Chinese name which I only dared to run in Windows after scanning it for viruses and malware, but it just hung without doing anything. Well, the pen doesn't require software anyway, although the right driver may enable the pen to be used as a webcam. Funny enough, there were also some photos and a movie of a kind of office that the seller probably took to test the pen.

Comparison of the spy pen with a normal pen
Here's a photo of the pen, compared to a real pen of the same ‘big business’ style. You may have a hard time telling which one of them is the pen I'm reviewing here. The thicker body and the small button are the only giveaways if you know what to look for. People will not suspect this pen unless you told them that you'll be filming them with a gadget. There are normal pens that are as thick as this one and nobody will ever find the presence of a button on the end of a pen suspicious. The weight is normal, the electronics don't make the pen suspiciously top-heavy.


Video/Photo toggle switch and USB plug
  • 4GB of storage: when unscrewing the pen at the middle, a USB plug is exposed, and the pen can be used like any USB memory key. 4GB is plenty to store the recorded videos and photos.
  • Video recording at 640×480 at a theoretical 30FPS: in reality, the camera adjusts the frame rate to the lighting conditions. In daylight, the framerate is about 17 to 20FPS. When it's dark, the shutter time is increased, resulting in a slower frame rate (down to 5FPS) to maintain image quality. Otherwise the signal would need to be amplified so much that it becomes more noise than image.
  • Audio recording at 8kHz: a bit of a disappointment compared to the video, this is barely above telephone quality. But, unlike most other pens which simply use uncompressed PCM, this one compresses the audio with the AMR codec at a bitrate of 5.6kbps, so it doesn't gobble up storage space.
  • Still photo camera: a switch located at the USB port allows to toggle between video and photos. The camera takes 3MPixel photos, pretty good for such a small gadget. The effective resolution is lower because there appears to be some interpolation going on, but the photos still look impressive for being taken with a pen.
  • Battery autonomy for 80 minutes of recording: I haven't tested this, but it's what the USA seller claims and they seem to have done thorough testing. They are honest enough about the pen's shortcomings so I guess their autonomy estimate is realistic.
  • Video time stamp: the date and time can be set by placing a file called ‘time.txt’ on the pen with contents “YYYYMMDDhhmmss” (like “20090502192500”). The pen will sync its internal clock to this file the next time it's powered on. The internal clock should keep on running unless the battery is completely drained or the pen is manually reset.
  • It writes! Yes indeed, it is a real pen. The ink refill is of course less than half what you would find in a normal pen, but you can actually spy on someone and take notes at the same time.

The videos are recorded directly in 3gp format, which is common for cell phones. To play these videos on a PC, various software can be used like QuickTime or VLC. On a Mac, QuickTime is normally preinstalled.

Performance / Quality

First of all, judging from the size of the thing alone, it is obvious that not too much should be expected on the performance front. I believe that what the designers of this pen did, is basically take the components that are used nowadays to add camera functionality to cell phones, and cram them on a PCB that just fits inside a pen, together with a tiny Li-ion battery (as you'll see below, I'm right about this). To keep the camera concealed, it has to do with a hole just large enough for a decent image but small enough to be inconspicuous. You probably wonder where the actual camera is, because it's invisible on the photos above. It's just above the clip. The intentionally overexposed photo below shows the hole with the lens underneath. It's almost a pinhole camera, but it does have an actual lens.

The 'hidden' camera

Using the pen is straightforward: it will boot up when the top button is held down for about three seconds. In video mode, it will start recording automatically a few seconds later. A tiny hole at the back shows a red light that blinks every few seconds to indicate it's recording. Press the button again to stop recording. Then, either press again to make another recording or hold down the button to power off. Taking photos works the same way, except that a green light is shown while the photo is being taken. Taking a photo takes a few seconds and I'm unsure when the actual photo is taken, so standing still is recommended. The video/photo toggle switch at the USB plug is tiny, but flipping it is easy with the tip of the pen which you'll be holding anyway. In case the pen would ‘crash’ or hang (which did happen quite a bit initially, see the ‘hacking’ section), it can be reset by inserting a toothpick in a second tiny hole on the back.

Here's a short sample of a video taken with the camera. If you enable YouTube's ‘high quality’ and view it fullscreen, it's pretty close to the quality of the actual recording. Or, you can download the original 3GP file here. More sample videos could be found on the (now vanished) EyeSpyPro site.
Unlike many built-in cellphone cameras, this one doesn't suffer too much from the ‘seasickness-inducing wobble’ which is caused by the fact that these tiny cameras continuously scan the pixels in the image (rolling shutter) instead of taking a whole frame at a time. But it's still noticeable when making sudden movements.

Sometimes, an intermittent ‘bleep’ sound is present on the audio. It can be noticed in some of the EyeSpyPro videos. This is one of the flaws of this device. The other spy pen models don't have this, but most of them have much worse sound overall. The bleeps are only audible when recording in a quite silent environment, otherwise they are masked by the audio itself. Most likely there is insufficient decoupling of the circuits within the pen, and the bleeps are interference on the audio circuit from either the processor or the memory chip. When the automatic gain control boosts the volume, the interference becomes audible. You can hear what the bleep sounds like in this MP3 file of a recording made in a silent room. I managed to somewhat remedy the bleep sounds (see below): the first half of this recording was made before my ‘fix’, the second half after.

Another flaw which is visible in my demo video if you know what to look for, are occasional video glitches. They can be visible as blocky artefacts (look at the distorted date stamp at 14:38:43), but sometimes a few consecutive frames get messed up almost entirely. The same artefact can be seen in some of the EyeSpyPro sample videos, more proof that this must be exactly the same pen. The cause of this could be related to the bleeps, i.e. interference, or maybe a bug in the software.

Example of a photo

Here is an example of a photo taken with the pen. It is downscaled, click it for the full-resolution photo (still recompressed to a lower quality than the original, but it should be barely noticeable). As you can see, not bad for a photo taken with a pen. At full resolution the photo has some kind of ‘artistic’ effect, which may be due to interpolation or high-frequency interference. The camera does a decent job at low light levels. The above photo was taken at dusk, and the camera can handle a whole lot less light. The photos become increasingly grainy with decreasing light, and the limit is about the light from a street lantern. Much better than my old Nisis QP3 ‘Pen Cam’, whose photos already went nearly black at dusk (it didn't look anything like a pen, but it was small and the closest thing to a spy gadget I had back back in 2002).


If you have this pen or a similar model and it has stopped working, don't go fetch a hammer just yet. The pen has probably ‘crashed’ due to the lousy shielding problem mentioned in the ‘hacking’ section. Most likely you can get the pen working again by resetting it. All these pens have a hidden ‘reset’ button, in the second hole at the back (below the hole with the indicator light). Insert a toothpick or other narrow object into this hole until you feel the ‘click’ of the button. If after this, your pen still doesn't respond nor show up when plugged in a USB port, then you should start worrying.
If it still works as a USB drive when plugged in a PC, but doesn't charge and doesn't power up when pressing the button, then the battery is probably dead. If it's the other way round, i.e. it still records video but doesn't give a sign of life when plugged in your PC, then the USB contacts on the PCB may be broken. You might be able to re-solder them after disassembling the pen.
Make sure not to completely discharge the battery and then leave the pen sitting discharged for a long time. This can kill the battery, so always charge it before storing it for a long time.

It appears that on some models of video pens, part of the software that makes the video recorder work is stored on the user-accessible part of the flash memory. This means that if you delete everything on the USB drive, the pen will not work anymore. If you buy a pen like this and it has special files on it, make sure to never erase them! Also, make a back-up on your PC or another USB drive, such that you can restore them if the files would ever get erased by accident. I don't have a pen like that and I don't have those files, so I can't help you if you erased them.

Looking inside and hacking it

Aside from the cool photos, this section is of little use to people who have never seen a soldering iron close by, or who already have problems mounting a picture frame to a wall.

Looking inside

I already disassembled this gadget within one week after receiving the package. There were various justifications for this madness: first, warranty would be a hassle anyway with something bought through a Hong Kong eBay seller; second, I wanted to see what it looked like inside; and third: I suspected that I might be able to fix or at least reduce some of the flaws.

On a forum I read that the most popular spy pen model, the MP9, could be easily opened by pushing the USB plug into the housing. This would cause the top with the button to pop off and the PCB to slide out. Judging from how the M-909 looked this was also the way to go, but it proved to be much more difficult. I managed to pry off the top with a knife and a screwdriver, and this gave me a look inside (see photo). But whatever I tried, the USB plug wouldn't budge.


Eventually I resorted to brute force: I placed a protective piece of plastic around the top, such that I could tap on it with a hammer without damaging the metal or PCB (see image). This worked at last. After the PCB came out I discovered that I had broken some kind of plastic tabs which had been glued to the inside of the cylinder, making it impossible for the PCB to move.
If you want to try this yourself, you should find a piece of plastic or wood that has a hole in it slightly smaller than the outer diameter of the pen. Or you could make such thing. After you have pried off the end cap that contains the button, place this ‘adaptor’ on top such that it rests on the casing of the pen (but not anything else). Then place the pen upright with its USB connector on a hard surface and start tapping the ‘adaptor’ with a hammer. If you're unlucky, your pen is glued shut really tight and you will destroy it, so try this at your own risk.

Now, the photo you've all been waiting for: what does this marvel of miniaturisation look like on the inside?

Electronics of the spy pen

As expected, a small Li-ion or LiPo battery (FYI: it's labeled D2-BEP-551240 220mAh - EMA), a tiny camera and microphone, and for the rest a bunch of SMD components that you'd also find if you cracked open your cellphone. It seems that the lower limit for the diameter of the pen is dictated by the width of the flash memory chip. The markings on the other large chip (the CPU) under the battery had unfortunately been removed, probably in case one of the crazier spies like me would be spying inside the pen instead of with it.

New microphone placement

In the end I did manage to improve some aspects of the pen before I reassembled it. First, the microphone was situated at a rather silly place, it sat at the very end of the PCB, on top of the pushbutton switch (see the first photo of this section). Any audio would need to reach the microphone mostly through the camera hole. In the MP9 the microphone is situated underneath a larger hole where the clip is fused to the body, but there was no room for the microphone there in the M-909, due to the longer battery. Nevertheless, I managed to place it there anyhow by shifting the battery downward. It's a small improvement, but with the already crummy audio we want to catch every deciBel we can. The photo at the right doesn't only show the improved microphone placement but also a nice macro photo of the camera.

Microphone capacitor hack

Second, probably the largest improvement: a reduction of the sometimes annoying ‘bleeps’ on the audio. I soldered an additional capacitor (33µF) in parallel with an existing one which seems to stabilize the voltage for the microphone. It works, although it only decreases the symptoms (you can hear the difference in this MP3 file: the first half was before the fix, the second half after). An even larger capacitor value could have been better, but this was about the largest one that would still fit. I'd rather have eliminated the ‘bleeps’ at the source, but I couldn't find any other accessible capacitor that might be an underrated decoupling cap. I also soldered an additional capacitor at what I believe is the decoupling cap for the CPU, but it seems to have little to no effect. I had hoped it would reduce the glitches in the video stream, but it doesn't seem like it. Maybe they're just in the pen's software.

Additional grounding point

And third, I provided a better grounding point to connect the pen's housing with the circuit's ground. The pen had crashed before on several occasions, especially when I had nudged the USB plug in my attempts to open it, and when unplugging it from the USB port. A shiny chromed surface pushing against the USB plug was the only ‘connection’ between the circuit's ground and the housing. My experience tells me that chromed surfaces are absolutely worthless as electrical connections. When the metal housing is disconnected from the ground, it becomes a huge antenna sending noise into the delicate circuit, especially if a human touches the housing. So, my little hack consists of a piece of wire soldered to a transistor's ground pin (indicated with the arrow on the photo). When the pen is assembled, this wire pushes against the metal wall, providing a good grounding point. The pen hasn't crashed since, I keep my fingers crossed...
Mind that the circuit layout for different pen models may be completely different. If you're going to try this hack on your particular pen, don't just solder a wire to any transistor near the reset button. Verify that whatever you solder the wire to, is connected with the outer part of the USB plug.

Lousy decoupling and shielding is something I noticed on other Chinese gadgets too. If any of you Chinese read this, please update your knowledge of good electronic design practices!
Re-assembling the pen was a matter of sliding the PCB back in. Due to the tight fit, considerable force is still required to move the board even without the broken tabs. It took me a few attempts, but I even managed to perfect the centering of the camera module respective to the hole, so the amount of ‘vignetting’ on the image is now minimal.


As in my other gadget review, here's a list of pluses and minuses.


  • You really can record covert videos with this thing, or take photos without people noticing it (which you shouldn't do unless you have permission). Even for less legally dubious applications it can be useful, like hands-free filming while skiing, or maybe even as a nose cam on a reasonably large RC plane!
  • Video and photo quality are pretty decent for a small gadget like this, and the video files take very little disk space thanks to MPEG-4 compression.
  • It doubles as a 4GB USB drive (there are even 8GB versions of some models).
  • It even works as a pen, who'd have expected that?


  • It's quite large, although real pens of this size are not uncommon. It may just look weird to always carry a pen that one would only use to sign contracts.
  • The video stream has occasional glitches.
  • The audio has intermittent ‘bleep’ sounds during silent recordings, possibly related to the video glitches.
  • The audio is only 8kHz sampling rate.
  • The pen requires some non-trivial hacks to make it more reliable, in other words the design could use a revision.

For the real gadget lover, this pen is recommended if you can live with its flaws. Even if you're like me and don't plan to spy on people all the time, this is still a cool gizmo on itself. If you don't care too much about the image and sound quality and just want a pen ‘that records video’, the cheaper MP9 may be sufficient. It might or might not be glitch-free and more stable, but it does have really awful audio. I'd rather have the occasional ‘bleep’ instead.


Update 2009/10/06: dead battery

It seems like my pen's battery has died: it refuses to charge, even though the pen otherwise works perfectly with a USB power adaptor. It appears that it's the battery's microscopic ‘controller’ PCB that failed, the cell itself is still OK. If anyone knows where I could get a suitable replacement battery (about 220mAh at 3.7V LiPo, dimensions 5x14x41mm), I'm interested. It should be cheap of course, otherwise I might as well buy the cheapest spy pen I can find and do a battery transplant.

Update 2010/04/07: donor pen

New el cheapo pen

Since it proved nearly impossible to find a replacement battery of the correct size, I went for the second option. I found a pen for €13.5 all-in to act as a battery donor. The reason why it's so cheap is that it has no built-in memory. Instead, you have to insert your own MicroSD card. This is cool in two ways: storage is not fixed, and the pen is less thick because it's no longer constrained by the wide flash chip. This pen is also able to take photos next to movies, although switching between these two modes is hit&miss because everything has to be done with the single pushbutton.
The bad news is that this pen uses the shameful and laughable practice of upscaling the photo and video resolution to make it appear a high-definition recorder. From looking at the images, it is blatantly obvious that the actual resolution for both photos and video is about 640×480. This does not only waste disk space but also boosts processing requirements, hence the battery doesn't last long. The audio is pretty horrible too, it is very noisy because it has only 8-bit resolution. So, this pen is both cheap and crappy, an ideal battery donor. I didn't even bother trying to take it apart cleanly: I cut open the casing with a Dremel.
I successfully transplanted the battery, which is somewhat smaller so I'll get less recording time. A test gave exactly 1 hour, which is still good (better than the other pen at any rate). I might put the other pen's innards into another tiny enclosure with a more readily available LiPo battery.

©2009/05-2010/04 Alexander Thomas