This is of course a hoax.  There is not a source of 'latent energy' in your water. 

The energy required to split the water into hydrogen and oxygen is greater than the energy you get back from the combustion when the hydrogen and oxygen re-combine.

This is a useful basis for storing energy (hydrogen fuel cells are being developed, and even deployed though so far in small numbers). Fuel cells do allow you to get your energy from your wall socket at home, to use an internal combustion engine running at a more efficient constant power output (eg hybrid cars), and to store energy from braking in order to use it to speed up again.  All useful stuff.

However, this techno;logy doesn't solve the problem of where to get the energy from as is claimed.