Odie,
this type of Hydrogen Addition has been around for awhile now. A buddy of mine back East works for a small company converting Vehicles to Hydrogen. Claims the Condensation collected from the TailPipe is Pure Enough for Human Consumtion(Probably Not recomended tho)
 You would think,if it was that practical of an alternative, you would hear/see more reports on it though????
 Let me know how that works out fer ya

They are playing on a gimmick or maybe two.
To convert water back into Oxygen and hydrogen you need to apply energy or use a catalyst. Using a catalyst is the idea behind what we know as a fuel cell , it's posssble but very expensive. I guess you could make one ? but I didn't see pictures of the guy with the Honda engine having one installed in his car did you ?
Back in the 70's when smog rules and no-lead lower octane gas came into effect there was a device that blended a small amount of water vapor into the intake system. it acted as a sort of an octane boost by slowing down the rate of combustion wich would allow pre smog high compression engines to run on lower octane fuel for daily driving I also remember them being installed on motorhomes to suppress engine pinging.