Tiger Direct has the Tony Hawk Helmet Cam for $49 after rebates. The framerate is 15 fps, but it's self contained, solid state and supposedly records up to 30 minutes (but I've read different articles stating from a few minutes to 40 minutes of recording). It comes with a 32 meg card, but I haven' been able to find out if it is expandable to larger SD cards.
There are some sample videos on this site The review is negative about the camera, but for our purposes, it may work out well... For $50, can we really go wrong?