You should check out the Scout helmet cam might just be the best one you can get for the money.
http://www.viotac.com/store/customer/ourgear.php?page=scout_overview
I ride downhill mountain bikes and agressive cross country I have one of these helmet cams attached to my fullface and my lid. Works great and I would recommend it.
if you buy it and then stop using it please keep me in mind if you go to sell it off.
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