I've had pretty good luck with a Sony digital camcorder mounted in my Extra
using a Bogen clamp mount. It is a heavy duty mount that held tight up to at
least 6+ G.

I used a separate lipstick mini camera for video input, mounted to my
helmet, but of course it could be mounted anywhere. I'm not sure whether
multitracking is possible with one camera, or whether you would need to put
two tracks together with some editing software like Adobe Premier.