Experiments on NFC with a simple home-build circuit: My phone's 13.56 MHz field delivers energy to a ST25 chip via a hand-wound coil, powering it up, receiving a simple command via NFC, subsequently waking up a Pico microcontroller that executes the command. In this case, slow or fast flashing of a LED. Firmware, PCB and 3D-printable case are open source.