Have a look, what I just found on German Ebay.
Here is somebody, that already uses water splitting to heat
and drive his car:
CLICK here: Cheap hydrogen generator (http://partners.webmasterplan.com/click.asp?ref=284148&site=1382&subid=&type=text&tnb=32&diurl=http%3A%2F%2Fadfarm.mediaplex.com%2Fad%2Fck%2F707-3922-3266-17%3Fmpro%3Dhttp%253A%252F%252Fcgi.ebay.de%252Fws%252FeBayISAPI.dll%253FViewItem%2526item%253D6060791802)