From the video link further down the comments it clearly states that it uses ultrasound at around 50kHz, which is then transformed back into about 30V, but I didn't pick up any information about how much power is actually transmitted.

As for safety, they state that it is above human hearing, and bounces off skin, so does not penetrate tissue like the high frequency ultrasound used for medical scans. Not too sure about the high freq claim, as some "ultrasound" devices give me a headache even though they are supposed to be above human perception.

The idea seems to be to charge a battery in the flash-drive sized charging adapter, and then use this to charge whatever appliance you plug into it. They mentioned about 3hrs for full charge for this adapter, but again, not sure how much power this equates to.