Screw bio-fuel, hybrid cars, and electric motors, how about the air powered car?

In my house we often debate the idea of what will be the next power source that will replace fossil fuels.

I have read various articles on all sorts of bio-fuels, hybrids, and even water powered vehicles, but if this thing is viable then we can essentially have a vehicle that has almost ZERO impact on our environment. How cool would that be?