The claim is bold: to be able to reliably and safely transmit energy over a distance of about one meter (~3.3 feet) using ultrasound, which is sound at a frequency higher than what humans (or dogs) can hear (cats could hear it, but only if one were wearing the transmitter). uBeam says the system is safe and containable, so no power is sent beyond the set range of transmitter and it will not interfere with any existing communication systems or electronics.
Unfortunately, that safety comes at a cost. Unlike radio waves, sound waves can't pass through solid objects. uBeam says that 99.9% percent of the emitted ultrasound will bounce off the skin, meaning the charger needs a direct line of sight in order to work. If you or anything else blocks the beam, you don't get any power.
Theoretically, if it is as safe as uBeam claims, you could essentially flood an area with ultrasound charging and get around anything blocking a device (aside from the hand holding it), but that would be a pretty big waste of energy. Still, this could be a very interesting technology as it matures, but there's no word on when we might see it starting to filter into commercial devices.