Power harvesting ...

Yes I wonder how many will remember the self powered AM radio circuits of years back :-)

Sounds interesting but I think there is a snag for the EU since as far as I'm aware the equivalent ISM band (868MHz) is not open for continuous transmission and I don't think at that sort of power level either. I imagine having someone transmit continuously at 3W ERP in any 'unlicensed' band may not be so popular. So perhaps we will see an introduction of a special RF slot dedicated to this sort of application and hopefully a global one. Or maybe we should recheck the energy levels harvestable by those old radio circuits, granted not so deterministic for different locations but who knows ...

thanks ... IIRC, the WRC, the body that meets to define what's allowed & not-allowed in the world of the radio spectrum, meets rather infrequently - 'wonder if it's already on their agenda for next time ?

Nikola Tesla came up with the idea in the 1890's . I think he lost his backing from J.P Morgan as Tesla wanted it to be free and his backer realised he wouldn't be able to make any money from it if this was the case.
See this wikipedia article.

yep, interesting article, it's one of the old dreams - what's changed, I guess, is that the electronic / digital / micro-processor revolution has improved precision & efficiency & volume requirements, and brought down the level of power that's useful, at both ends - transmitter & receiver - plus a strong-enough desire has developed in enough people for an alternative to a cobweb of wires !