Spypoint Tiny wireless. Let them steal the camera. If you've hidden the receiver, they'll never find it. Yeah, you'll be out $200, but you'll have their pictures.
You can purchase trail cams that e mail photos to you. They are pricey but might stop theives. Friend of mine bought some after some theivery of cams.
I like the razor blades under the dash idea. The way I see it, don't try to steal my **** and you won't get hurt. Cut fingers would be a blessing compared to what I'd do when catching someone trying to steal my vehicle.