Filling the tires on demand, is something i was thinking myself. but as the tire continuously moves, there must be a valve with the brake housing. but the valve must have a rotating pipe which could fill the air on demand.
well, if it's already in application with some cars then, more can be found from that design, if it's not yet invented, then some one should work on prototype.
although i like your idea, whereas it is from bond movie.