I have one of the Sony "bullet cam" kits, which I bought from
Sports Camera. While the lens is amazing quality and I love the results, the problem is the rat's nest of wiring you need. A portable DVR is required to capture what the camera sees but in addition to having that fag box-sized gadget slipped in your pocket, you have wires to the camera, to the separate microphone and to the separate battery pack (6 AAs).
I have lots of footage shot from a platform on the tank of my R1 but most of it is a bit hairy to post on YouTube. I may get round to editing some and I have to say the quality is superb. We discussed the set up
on CC here where I add my thoughts on page 3.
The bottom line for me is, while it's excellent in a fixed position I find it very fiddly and frustrating to set up for rides with wires everywhere. I have ordered a Muvi for sheer simplicity - Oh and it's about a quarter of the price I paid in 2006!