A few months ago, helmet mounted cameras were talked about on here.
I bought one from China off eBay sold as:
8GB 120° HD 720P MINI DVR ACT20 Waterproof Helmet Camera Motorcycle Bike Cam. Less than £50 with a card.
I also had a look at the pictures that come off the non HD version. HD version - number plates easily readable, non-HD ... need to be close and in the right light so not as useful.
I mount the HD one on my helmet every bike ride and the record time of about 3 hrs is plenty for me. If I do longer rides, I stop to flip over the micro SD card.
Long story which I won't bore you with, but I called police over an incident with a car and the camera was invaluable ..... paid for itself many times over.
Commuter, racer or casual rider: I thoroughly recommend you look into it. If enough of us do it and report idiots, it could make a difference! Imagine if car drivers think they maybe recorded ...safer for all!!
p.s. I respect your right if you don't wear a helmet. Put camera on your crossbar.