Techmoan - Techmoan
There's a lot of smaller, cheaper action cameras out there. I have a Mobius, works well. There's also even smaller action cameras sold for mounting in R/C aircraft. I wore one of those on my bike helmet for awhile, it was smaller that a matchbox.
However, don't let the idea that you're going to capture cool video lead you to do stupid stuff.
I cycled up Mount Diablo once and then switched on my helmet camera for the descent. After 1/4 mile I stopped and turned it off. I was going harder into turns than I should have, just to get cool video. Rode the rest of the way without video. Bummer really, that is a super fun descent, 10 miles of curves and on a road bike, you can really fly, I was passing cars in the curves like they were tricycles.