This is either a hoax or a scam; determining which would require looking into the heart of this sales person."Claimed water fuelled engines often obtain hydrogen by electrolysis of water. The electrolysis cell must be powered electrically. The hydrogen and oxygen obtained by this electrolysis can then be burned but more energy is required to drive the electrolysis cell than can be extracted from the resulting hydrogen-oxygen mixture. Otherwise, such a system would be equivalent to a perpetual motion machine." - http://en.wikipedia.org/wiki/Water-fuelled_car
My friend first saw this on the Discovery Channel and then saw it later on one of those car mechanic shows. I guess I'll find out, he is going to try it.