The Mini DV 80s is a tiny (2″ high) clip-on action video camera. My japanese is super rusty but it seems to have a 2 megapixel camera with a 72° field-of-view that can shoot in 1 lux. It records video using Motion JPG at 640×480 at 25 fps and the battery is good for 2 hours of video and sound recording. It writes onto a microSD card (up to 8Gb) and burns through about 1Gb of card space every 40 minutes. It also doubles as a web cam.
It works in temperatures ranging from -10°C to 60°C, takes 2 hours to charge and weighs all of 50 grams (2 oz). When you’re done, stick it into a Windows (2k, XP or Vista) USB port (1.1 or 2) and download. The other cool bit is it comes with different mounting kits. You can hang it off a lanyard around your neck, clip it on your belt or jacket, or even hard-mount it to a bike or a helmet. There’s also an arm band for you runners.
UPDATED – It looks like you can pick up an almost identical product, the Mega Mini Spy Camera Pro from Brickhouse Security
Thumb sized smallest class/Voice activated recording/Attachment brackets for bicycle helmet included/Also doubles as a webcam