NFC is used at much higher power usually. If you think of the labels on clothes with RFID chips in stock and a reader operated from 1m or so distance. It's als

NFC is used at much higher power usually. If you think of the labels on clothes with RFID chips in stock and a reader operated from 1m or so distance. It's also NFC, kind of.. I think that NFC for paying with smartphone is operated at very low power for security reasons. Other possibilities without RFID might be a photo diode and a led in the finger of the robot sending light encoded data (filename ending *.led, format needs to be defined)