Within the time that I have spent on this forum (number of years coming back NOT number of hours spent typing), I learned that radio was power transmission. I have never seen it happen, but some have told me that light bulbs can light up within the control panel of a radio stations transmitter.
An antenna is nothing more than a receiver of power. The more powerful the signal the more power received.
Turning that power into something storable????
The more effective this method is, the more holes that will be created in the wifi network. Little places that the signal disappears.
There is at least one gadget already in existence, an air pollution monitor, that does something like that, it charges up a battery by harvesting radio frequency energy from existing wireless and broadcast networks. The technology is called "Freevolt" and is described in this news story from 2015:
The gadget is manufactured by the British businessman Paul Drayson, who donated considerable sums to the Labour party when Tony Blair was in power, and as a result got made a Lord and subsequently did a few government minister jobs.
It sounds like Apple are attempting to do something similar with mobile phone charging, and as they are talking about their own patent applications, it looks like they're not using the Freevolt technology.
Drayson's air pollution monitor is on sale through Amazon UK:
It looks like the monitor is actually a carbon monoxide monitor, and it uses carbon monoxide levels as a proxy for pollution levels in general. Some of the customer reviews suggest that the monitor doesn't work very well in practice.