Many camcorders have a time lapse mode where they'll record a bit every couple seconds and so can get hours of video on a 30 minute tape. Mine is 7 years old and was a mid-level model when I got it, and it has that feature. Set it up on a tripod where it's indoors and protected and can see the car. Then when you're watching the tape back after you find fresh footprints you can fast forward through it to see who the bastard is...
I'd also recommend either leaving a light on where the car is parked at home or getting a motion sensor light to cover that area. Most delinquents don't like light. There's motion sensors that screw into regular bulb sockets for cheap.
You could also just put a sign on the windshield and back window saying "this car under video surveilance" - might be enough to keep the jackasses at bay.
Good luck.
Scott
