Here's my low budget solution. My daughters low end Hitachi DVD camcorder. It records on 30 minute DVDs. So you essentially have to change out a disk per session. I hook it to a cruisecam.com mount which clips to the headrest mount. I think the mount was about $50. I put it on the driver's headrest so it's looking right over my right shoulder. It's quite adjustable for angle and position left and right.
Next problem is the camcorder battery, since it only lasts about an hour, I hooked up a small (350 watt) Radio Shack power inverter in my trunk which I previously secured with duct tape and cable ties to the bar that was next to the battery in the trunk on my E36. However for my E92, I'm going to use those metal pipe sinching things (can't think of the name), and secure it to just above the HD radio mount. (on my car with HD radio, left side of trunk, there's a plastic tray, I'm going to pull the tray out and secure the inverter to the metal mount for the radio.) I'm going to use this set up for this weekend and I'm going to hook it up tomorrow night, so I'll take pics.
I haven't done this in my E92 on the track yet, so this is the first attempt, however I did some test fitting tonight and it seems like it will work.
Here's some video using this setup in my E36. Perhaps not wide angle enough, but it's good enough for me. For the most part the camera is pretty steady, even on a rough track like Summit Point.
Here's some video using this setup in my E92, not on the track.
Not perfect, but it works great and it's low budget.