As always, if it sounds too good to be true, it is.
Hydrogen generators are nothing new... they have been used in low-pressure stationary applications (such as in laboratories) for dogs years. You pour in water, you plug 'em into the wall, and via electrolysis out comes hydrogen (plus oxygen, which you can either waste or use). This guy's mumbo-jumbo "HHO Gas" is nothing more than the hydrogen gas and oxygen gas streams mixed together (which, of course, burns like a sumbitch when ignited, producing nothing but water).
Since the laws of thermodynamics dictate that no real machine can be 100% efficient (and, in practice, even 50% efficiency can be a stretch), the energy you get from burning the hydrogen plus oxygen is less than the (electrical) energy you consumed to generate them.
H generators are convenient because dealing with high-pressure compressed H cylinders is a huge pain. H under pressure is notorious for leaking through even the tightest gas fittings and valves, so a high-pressure H cylinder doesn't stay pressurized very long.
Although it is hard to judge from the typical crappy tech reporting in the Fox News video, here's what I suspect is going on: This guy has had the (superficially, at least) clever idea of using a hydrogen generator in an H-fueled car, rather than the usual H gas cylinders. On the surface this might sound smart, because one of the greatest problems in developing H-fueled vehicles is that you don't want people driving around in cars containing 3000 PSI H cylinders... it leaks, and when they crash you have mega-bombs (a hydrogen explosion makes a gasoline fire look like a Zippo lighter). But if you restrict the vehicle's H storage to LOW pressure, you can't pack enough H into the vehicle to operate over sufficient distances (at least by American standards). This is H-cars' Catch-22, and a lot of smart people have spent a lot of time trying (mostly unsuccessfully) to address it. This guy is right in that water is a very efficient way to 'store' hydrogen. But he is clueless because it will require a lot of electricity to liberate that hydrogen from the water... thus requiring a lot of batteries onboard... and the less-than-100% efficiency of electrolysis means that what you'll end up with will be, essentially, an electric car that is less efficient than conventional electric cars. Duhhh. Better to just use the electricity directly to power electric motors... more energetically efficient, and fewer parts.
This guy's real accomplishment is that he has breathed new life into an old scam ("fuel your car with water... the amazing power source Big Oil doesn't want you to know about!"). I can't get too upset about him... there's one born every minute... but I am really ticked off by Fox News and others covering this story, who have done zero to present it thoughtfully. It makes for a sensational headline, which is all they care about, so they go with it without asking the most basic questions. Grrrr... .
Attention: TDR Forum Junkies 
It burned. 
I hope I win for best supporting role. 
