But, looking in to it, there seems to be a whole lot of competition getting in on the act, including Sony and Bullet. The new Sony Action Cam looks pretty good for bike use.
One aspect of that camera that looks useful is it has in-built Wi-Fi, so you can upload footage without going near a computer.
If you do splash out on a camera for on-bike capture, there are a couple of tips Ive learned from irritating experience. Make sure you test it on a longish ride before you do anything special that you want to film. Pay particular attention to the adjustment for the view you get, any smears on the lens cover and listen to the sound recording carefully - sometimes you can get rattles that overwhelm the ambient sound (engine and exhaust) and you'll need to work out where it comes from.