best helmet cams going around these days?

Hi guys,

I do a bit of extreme outdoor sports, karting, cycling, motorcycling, kite surfing and have always thought it would be cool if I could get a helmet cam.

Just wondering if anyone around here has experience.

I cam across the contour hd camera
http://contour.com/

looks the goods and relatively inexpensive, don't know about interchangeable lenses etc.

Just to save me risking putting my 5d on my helmet etc.

Any help would be great