What he probably did was use sound to create cavitation in the water, like an ultrasonic cleaner. So the water wasn't actually "boiling" (as in heated), but still had lots of bubbles. If he was able to boil water with less energy, you could use that technology to create free energy, which would have limitless applications. I doubt it's really boiling water, unless the amount of energy being put into the creation of the sound is at least equal to the calories required to boil the water conventionally.