a lot of smash and grab guys use something called a "ninja rock" which is a chunk of porcelain from a spark plug. throw it against the window and it explodes. if you have tint, it is like tape on the glass, so it doesn't break apart as easily and makes the smash and grab operation take longer.
I've jerry-rigged one of those onto the bottom of a pepperspray canister. This "device" works wonders with drivers who think they can just run a cyclist off the road.