Been riding about 35 years and running a camera on my bike for about 5 years now, started with a cheap digital camcorder clamped to the handlebars with a Manfrotto quick release clamp, then moved over to Contour cameras.
I have a ContourROAM2 helmetcam for use on the bike and personally it is pretty much perfect for the job:
1. The glass in front lens is removable.
2. Waterproof to 1 metre.
3. Three hour battery life, removable would be better but would probably affect waterproofness.
4. The camera body is metal so should survive an impact.
5. Because the camera is shaped like a bullet rather than a mini digital camera it is lower profile and you don't need to stick it on top of your helmet and hit door frames when you walk through them.
6. The camera within the body can be rotated to level up the image, with a laser line to check the level.
A couple of improvements I would make to the ROAM2:
7. Add a decent sized eyelet that I can attach a 'proper' safety cable to it. The original clip that comes with it feels week, instead I now have a short length of stainless steel wire with a carabiner on the end that attaches to the chin strap, so if I have an accident the camera should stay with me even if knocked off the mount.
8. A removable battery would be good.
For a fixed bike recorder I would pretty much like the same as I would like with a car but waterproof.
1. Must do 1080P recording.
2. Instead of having the recorder and camera in one unit I feel it would be better to plug the camera into the recording box, which could be hidden within the back box or under the seat. This would mean that you would have camera options to suit your needs rather than one size fits all, like widescreen or normal lens, or the camera could be drilled into a fairing. Much better for security too. I feel this solution would be good for car cameras too, heat would be less of a problem if you can make the unit a little larger and/or add a heatsink too.
3. The ability to flip the image on the horizontal/vertical axis. A friend tried to setup a camera on their bike that was based on a reversing camera which meant that the image was confusing when viewing it normally because the left/right was flipped and words were reversed, with a few simple options this wouldn't be a problem.
4. I know a few people(non-bikers) that feel GPS is a great idea, personally I am not convinced about the positives on a motorcycle. Motorcycles often exceed the speed limit, after an accident it is possible to argue that the actual speed just looks a little fast because they are not used to riding a bike. Having a video that shows you are speeding in the event of an accident I feel is a bad idea. Also in the UK at least, the police can seize the memory card if they feel that it has evidence of an offence, without GPS the speed in a video is open to argument in court and you could muddy the waters a bit arguing that TVs are 25/50fps, the camera is 30/60fps etc, it won't stop a 100mph in a 50mph zone conviction but it might save a 60mph in a 50mph zone from conviction. Having the speed on the video will just prosecute yourself.
5. Having the camera config saved as a txt/cfg file on the memory card that can be edited via a text editor if required.
6. One I have always wondered about is a feature that is on CCTV cameras, why not switch to black/white during low light recordings. In the event of an accident your main goal is to get evidence of what happened, the fact a car is dark red or blue is much less of a concern than gathering usable evidence.
As mentioned above:
7. Auto start/stop when the bike is started.