The thing I wonder about are unintentional receivers. Metal rings that pick up eddys and turn it into electricity that just runs around in circles will cause the metal to heat up. Nipple rings that turn into spark gaps. A never ending list of hilarity!
The reason these problems don’t occur with Qi chargers is that the phones and other wirelessly charged devices have NFC chips in them that talk to the chargers and say “OK, I’m close enough, turn on and charge me.”
