CruiseCam Camera MountEarlier this year I got a CruiseCam mount for in-car photos. It works in any car with 2 exposed posts on the headrests (which excludes Volvos, or highback seats like the RX-8).
I had started to make a similar one with some aluminium square tube, but at the point where I tried to find a good, cheap adjustable camera mount for my project I finally admitted that it was actually cheaper & better to just buy the actual CruiseCam. This thing is very well designed and built. It attaches securely, is super easy to install/position/remove, and the camera mounting platform stays adjusted where you want it without vibrating out of place. It includes a safety strap if you feel the need to use it - I didn't, and removed it.
There's a heavy rubber guard that you have to slide out of the way to tighten down your camera, then slide it back into place for vibration dampening. My only complaint is that since the mounting platform is slightly textured metal, it could scratch the underside of my camera if I weren't careful. I solved that problem by putting a strip of masking tape (3M Blue Painter's Tape) on the mount.
On the A3, the front headrests always have a little bit of the posts exposed. In fact, it's just enough that the CruiseCam never touches the upholstery of the headrest at all, nor the seat since the plastic headrest fittings on the seat act as spacers. Absolutely no risk of damage to the car at all.
The slots in the back of the mount allow for whatever spacing your headrest posts have, and allow the mount to positioned side-to-side easily. You can also turn it around so the mount is on the right side of the passenger headrest, slide the seat back (and/or tilt the backrest slightly), open the right rear window, and adjust the mount so the camera is sticking out the side window. I would definitely use the safety strap if I did that! Of course, the mount also fits on the rear seat headrests if you want to mount it there (for example, for rearward-facing photos).
For some examples of it in use, see my first autocross article. All of the in-car shots were from my Canon G9 mounted on the CruiseCam.