On the bikes, we use a camera system which integrates into the comms system, which means you then get voice commentary directly to your video. We use a Sony P550 bullet camera which is the highest specification and is used in military and surveillance applications. The camera has the widest angle view of any available and, although short of human peripheral view, still very effectively puts the viewer into the picture.
This is connected to a mini DV recorder which records directly to an SD card. If set on low resolution (640x480), you get about 8 hours on a 4Gb card. The camera can, however, be set on high res which will give you DVD quality footage at about 1Gb/hour.
In England, I used a splitter which meant I could connect 6 camera's to the DVR. With the camera's mounted in different places on the bike, I was able to get front, rear, helmet (front/rear), belly-pan and tank mount footage. It was a simple case of switching between camera's on the splitter box to determine which camera would be used for recording.