Here you go, the camera keychain. What you use this for is your perrogative but we can tell you all about it.  You can find the spy camera at an online store called GeekStuff4u for about $175.  In short, the keychain has:

a small camera recorder in the center of Key Holder and 4GB internal memory to record everything with a simple push of a button [GeekStuff4U]

AkihabaraNews did a review on the product and in short, here is what they had to say:

• Camera has 4 buttons (only two are effective and will either start or stop recording video or take pictures
• It doesn’t come with an instruction manual so you need to know that the buttons that work are the ones close to the camera.
• It is easy to use: press the button one time for pictures, press and hold on the same button until the LED light stops blinking to record videos.
• Pictures and video are not bad [Look at the sample below]

[Source]