Problem with helmet cams are the users generally move around so much and look all directions and the head constantly bobs that it makes people queasy like being on a ship.
But for the money the oregon scientific is not a bad unit depending on what you are doing, it obviously won't give you pro video, but it's a pretty good solution.
Not my auction, just an example
http://cgi.ebay.com/WIRELESS-HELMET-CAM-CAMERA-ATC2K-ATC-2000-AT18-ATC2000_W0QQitemZ320248574752QQihZ011QQcategoryZ48514QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Specifications:
Movie Storage 640 x 480 pixels (30 or 15 frames/second)
320 x 240 pixels (30 or 15 frames/second)
160 x 120 pixels (30 or 15 frames/second)
Resolution 640 x 480 pixels (VGA QVGA)
Size 4.25L x 1.75D x 2.25H (in.)
Built-in memory 32 MB
SD memory card drive Supports cards up to 2 GB
Image format JPEG
Movie image AVI
File format interface USB (1.1)
Timer 10 seconds
Status LCD 2 digits, B & W
Focusing Fixed range from 1.5m~infinity
Deleting images All at once / last one
Auto Shut-off 30 minutes
Batteries required 2 AA Alkaline Batteries
Operating system Windows 2000/XP