Seems like dark tinted cars would have something to hide?
At the very least, a stealth installed alarm that pages you would be a good investment. Sounds really basic, but a lot of the cars reported stolen on this board didn't have an alarm. Obviously they can just pick it up with a tow truck/flat bed, but if you've got something that pages you and you're in the vicinity, you might be able to make it back just in time to see them haul your car off?
Always try to park with your wheels locked facing something so they'd have to bang against the curb/another car to do the above^
You can always try covering your car in gaudy glitter vinyl with a busted body kit to make it so unappealing that thieves would vomit on themselves on the spot and leave/die of dehydration?