back in 2015 some researchers came up with an e-ink display device which was powered entirely by harvesting joules from the NFC connection your phone used to talk to it, and I’m honestly kind of shocked these aren’t all over the place now? http://www.alansonsample.com/research/NFC-WISP.html
@ticky for what purpose? I guess they could be nifty rewritable labels on keys or sth but I don't see any super-obvious use case
@noiob @ticky My own method of doing so has been connecting Pi Zero Ws to a display via GPIO pins, scraping image data from a web daemon are home. Hardware cost is ~$60 per tag though, which isn't cheap unless you buy bulk supply.