I think there was already a thread about this somewhere, but I can't find it so I'll post it up:
Tata motors already has plans for producing these cars for India, and in a year or two, North America. The car has a range of up to 1,000 miles, and it costs about $5 to fill it up, and all this for under $20,000. Unfortunately, they look terrible.
From the Youtube Videos:
There's two engine designs; the one made in France is like a typical internal combustion engine, but instead of fuel and air, it's just air being forced into the cylinder to push down on it. In the vid, it sounds pretty loud, and looked slow. They also have a gasoline fuel tank in there, and for longer trips, it would run the engine very lean and get very good efficiency. The engine is 80% aluminum, so if the combustions get too big (above like 650*C), the block will melt.
The 2nd vid is from Australia, and the engine is similar to a rotary engine, only weighs 13kg, and has no transmission. The guy has put the engine in go-karts, little trollies, and cars. They show a vid of a go-kart running on compressed air towing a full sized car, but just barely. If that's the same engine that goes into the car, it would probably be very slow. The guy is working on a 6kg engine.
It looks like a good concept, but I don't see it getting off the ground. Most major companies have already spent millions of dollars researching hydrogen fuel cells and electric vehicles, so they'll just ignore this.
EDIT: Those vids are like 2 years old, so things would have changed by then...
Here is a more recent video:
-- this is basically an update to the first video (the French car).