I've used the GoPro Hero HD on my helmet, but actually never inside a helicopter. It is actually an outdoor action camera, but the autofocus mode can be changed so it works well inside too ("like if you are filming from the inside of a rally car" according to the user guide, this would make sure the camera doesn't focus on the close objects like the dash board).
It's a wide angle lens, with the best image quality I've seen for an action cam (different HD modes, also 60hz mode), and there are plenty of mount kits that you can get for it (suction, helmet, straps, mountain bike, chest mount). Not sure how it mounts on a headset though. Might be tricky to get it to stay in place. But to be honest, a fixed camera looks much better than one mounted on your head in my opinion.
Search gopro here on pprune and on youtube, you'll find plenty. And check the official web site for the mount kits.
Fixed position:
Helmet mount:
Last edited by Runway101; 6th Jan 2011 at 00:21.