My current helmet camera is a Drift Innovation HD 170, and I'm very happy with it. It takes great footage, and is very easy to use and is small and compact.
Battery
Make sure you set the LCD backlight to go off automatically after 5 seconds, that will greatly improve how long your battery lasts. The default battery lasts about 4 hours. I got a larger battery and that lasts about 6 hours of usage.
Storage/Memory
It takes normal SD cards, and can take 32 GB, but I've only se up to 16GB. You'll get several hours on a 16GB SD card.