I had an idea (which probably isn't original) that electronics could harness power from a signal or a wave (like a radio wave) or a ray or something like that instead of having to charge or buy batteries. How possible is this and what could be used to do this?
This would be along the lines of solar powered electronics, but what about other sources? Something that works like a solar panel that collects the rays or waves and converts it into electricity. Is there anything like this available or being worked on? Even something that used to be worked on but was forgotten.