If you get to see the unedited version of this video, the guy admits that it takes more radio wave energy to electrolyze the water than you get reburning the hydrogen with oxygen. This video brought to you by the perpetual motion conspiracy theory fringe on youtube.

Yes that’s true Ralf but i believe the solution is in the works.
Here is a sample of information found at this link.

http://news.nationalgeographic.com/news/2007/09...;

For now, the most immediate potential technology application is desalination—the process of removing salt from water—because the water formed after combustion is free of salt and other contaminants.

Scientists have known for a long time how to split water into its two elements, oxygen and hydrogen. But the problem is that the process requires electricity—typically derived from fossil fuels—which makes the process counterproductive and expensive.

“That would be a remarkable source of hydrogen and then you could either burn the hydrogen directly or use it in a fuel cell,” he said.

Aha Perpetual Motion one of my favorite subjects :)