inki now supports NFC-based command triggering via an ST25 chip. A phone tap provides RF energy to write a command payload and wake the device from power-off — no button needed.

See also https://hackaday.io/project/205461-harvesting-nfc-energy-to-transmit-commands  Hackaday Green Powered Challenge: the data transmission runs entirely on energy harvested from the phone's NFC field, with basically no standby power consumption.