I don't see why people just don't fast-charge their devices in the microwave. It would be a lot faster, and almost everyone has a microwave already.
Jokes aside, I'm not completely sure how the technology works, but if it's just picking up wireless signals at 2.4GHz and 5.8GHz, I kinda have to wonder if a transmitter would really be needed. Most places are already saturated with these radio signals. Would it be possible just to figure out a receiver that can just take energy out of all the existing signals out there? You're not talking about it needing to have data encryption and security, just be able to take energy from those radio waves.