Originally Posted by MaxF
As for the helmet cam: have a look at the Drift HD Stealth.... really good HD helmet cam with (if I remeber correctly) a plug for an external microphone (although you may have to also get this from the manufacturer).
Acc. to its manual, you can use a special external mic which is sold separately. Unfortunately, you can't close the dust cap with the mic connected. That's fine if the cam is fixed to a roll cage in a car, but calls for trouble on a bike.
All other cams I know have similar problems.
The VIO POV cams also allow for an external mic. Again, the dust cap can't be closed, but this system has the electronics separated from the lens. This way, you may be able to keep everything but the lens in a clean pocket. Oh, and they use a standard 3.5mm mic jack. www.vio-pov.com