I am building a rig to take those blurry background shots you see in magazines that manage to keep the car tack sharp without the use of another car.
I have a the camera mounted to a flexible lighting stand and a grip around the headrest for the test shot below. I have a couple of 5 foot poles to get the camera further away from the car and will use a wider lens and drag the shutter a bit more. I am awaiting some strong magnets so I can attach them to the pole that comes out from underneath the car. The second pole will come away from the car at an adjustable angle. The lighting stand then mounts to the pole giving me plenty of adjustment.
More to follow when magnets come in.
Something like this would be good