how about a small pod like thing with 4 cameras on it, that you mount upside down in the roof of your car where the overhead light usually is.  the cameras would record video of all angles of your car for accidents, police abuse, or anything at all.  It could have a small hard drive on it that records a set number of hours of video, or for a monthly fee, it would upload it to the companies servers where they would archive it and you could search it and stuff through an online interface.