Okay, haven't visited this forum for a while but just seen this thread.
From my username you'll see I'm a biker (Pan referring to a Honda Pan European) and presently using a helmet mounted Sony AS15. It produces great video and I'm quite happy using it. I had to make the mount myself because Sony have only recently entered the action cam market and not many accessories are available yet. When mounting on a helmet, you need to be able to adjust the camera angle in all directions. A wide angle lens can also be filled with helmet if mounted too close to the side of the helmet. This is why I used a ball joint mounting on my present setup.
I record all the time I'm riding. To save an event, I have to trawl through my vids at the end of the day and that can be a pain! I keep my daily videos for no more than 2 weeks ( in case I need to challenge a speed camera, lol).
Forget about mounting on the bike - too much vibration on most bikes - plus it needs to be removed every time it's parked. Helmet mounting is the way to go. The neck automatically tries to stabilise your head so the eyes can focus (ever watched a long-necked bird flying?). Okay, our necks are not that long but a degree of stabilisation is going on.
Mounting on the bike does not allow the camera to pan sideways. This means you can miss a registration number. I know a few of my vids have my head turning to catch the reg. number or a view of the driver.
I started with a key-fob 808#16 camera with a wide angle D lens mounted *inside* the helmet, above my nose and eye line. This means it's discreet (none of the tedious "What's the camera for, Mister?" questions). It doesn't need to be weatherproof behind the visor, it's lightweight, little air resistance (drag), and a battery pack can be velcroed to the outside of the helmet or dropped into top pocket.
See my video here:
and some video shot with this setup:
However, to get 1080p quality and smooth "Steadyshot" stabilised video with good night time performance, I bought the Sony AS15 and put it on the side of the helmet. Always on the side - not on the top 'cos you look a plonker and I'd smash the camera on door frames at 6' 3"!
Here's how I fitted it:
and some video shot with this setup:
I tried a wired bullet cam but found the quality lacking and the stiffer than normal cable a problem. A bullet shaped cam with front and rear lenses might be an idea?
Another requirement for many bikers is an external mic. that can be placed in the helmet - wind noise is a problem.
Vlogging (Video blogging) is becoming quite popular among bikers - just look at the YouTube Vloggers (Yes, there's some rubbish stuff on there - but you don't have to do it)
Blimey, it's late and I've been going on too long! C'ya later,
Paul.