I was trolling around on an RX8 board once, and one guy who lived in NYC had the same concern, so he posted about this stuff by 3M, its like a thick plastic adhesive cover type deal. You can get it applied to whatever sections of your car you want, its clear, and probably not too obvious. I'll try to find a link. I believe he had it done at an authorized shop.
EDIT:
Here it is.