At 2:38 you can see a pretty clear schematic. The principle appears to be: energize the outlet at 24VAC when idle, and then measure the load when it connects to try to detect human contact. if(!human) then switch to 120VAC.
Does it have any advantages over GFI (which is not mentioned in the video)? In an isolated environment (no ground paths), it could be possible for a human to become the load without triggering GFI. By plugging in a severed flex without a safety earth, for example, or in the scenario the developer demos with the plug-in Edison socket.
Which doesn't answer how to discriminate human loads. My guess is that they use an assumption that skin contact to an energized terminal will have an unstable resistance and capacitance. So if the measurement of R+C at 24VAC doesn't converge within .5s, do not switch to 120VAC. A consequence of this is that whenever a "legitimate" load is present, the safety feature is off and electrocution is possible.