I've mounted cameras on helmets lots of different ways, but a year ago I decided to build one right into my Phantom helmet to make a totally snag free "stealth" camera. Given that every smart phone has a tiny video camera built right in these days I'm surprised that no one (that I know of) does this. I've attached three photos of the result. The camera is in the forehead under the visor, although the image quality was ok though the visor I've since drilled a hole, two less surfaces to keep clean. An extra quarter inch of foam around the camera and circuit keeps it from touching my head. I mounted the lights where they can be seen on the chin, and keeping with the stealth theme added two screws to the front grill which are actually the power and record buttons. The battery is in a pouch inside the back neck padding. I built it from a Replay XD which wasn't easy and it isn't really a wide enough lens for "inside" shots. A better camera for this job might be the Mobius since it seems to be made to be hacked. It's fun to surprise jumpers after with a video, I always jump a camera now - if I choose to turn it on.
Dave