MoreCooler.com: It's more cooler with the thing

This one is too more cool to just stick in my links (plus, don't know how long the vid will stay up). It's glass that's bulletproof from one direction, but allows you to fire THROUGH it from the other (it even reseals itself)!

A brief presentation on how it works is at the end of the demo vid below.

Article about the glass
Demo video

Edit:
Website for the manufacturer w/more info

I bet it would be pretty ear-shattering to fire from inside a patrol car with the windows up, though...