I have a Contour Roam camera strapped to my handlebars. I bought the camera after getting hit by a car on the Lincoln Memorial circle. I was the fifth bicycle in a pack of five. I had lights and high viz. I was doing everything by the book - and still got hit by a distracted driver - and the police issued no tickets (the insurance company, however, negotiated a settlement easily). I thought - never again.
The Contour Roam has a nice form factor, fitting easily on my handle bar. It takes a micro SD card so basically you can have as much memory as you want. The battery is not bad; needs to be charged every day (my commute is 1.5 hours total - if I dont charge the camera, it will last some of the next day but probably will not last the full day).
The strap that keeps the camera on the handlebar broke; that's bad. As a result, the camera went flying off my bike and into the road - its still working just fine! That's good! It's a pretty reliable piece of equipment.
I have seriously thought about getting one for my car as well for pretty much the same reasons.