You could get a power pack for an electric fence or maybe one of those huge car audio capacitors to provide a good jolt, maybe even rig something up with a Tazer. For it to shock, you need to have a charge built up that can discharge immediately. I would run a wire to the wheel well with a quick release connector, then have a wire running off the cap that would reach. (You wouldn't be able to drive the car with a wire on the wheel, so you would remove the cap to drive.) Make sure the cap is insulated from the wheel, if it is grounded it won't work. Then set up the hidden camera, because it'll be funny as hell! This would also teach any dogs that try to pee on your wheels.
