It's a receiver that doesn't require a power source, but to say change the channel on a TV, it needs to be connected to some sort of transmitter that DOES require a power source.
You see, you can put this device IN THE TV as part of it. Now you don't need a standard battery powered remote control.
Then what would be the point of it not requiring an external power source if it's built into something that does?
Also, "The prototype could correctly identify the gestures more than 90 percent of the time while performed more than 2 feet away from the device."
I prefer sitting much more than 2 feet from a TV. There are already powered hand gesture systems with much better range that can be built into a TV.
Wow, that sure took a lot of thought!
Obviously it didn't.