[Richard]’s experiment with a motion-powered AirTag fits this bill ... The setup is minimal: an ESP32 microcontroller, an MPU-6050 IMU, a transistor, and some breadboard magic.

All you need is an Arduino, a motion sensor, a few wires and headers, and the code provided at the site below. Hit the link to see step-by-step instructions on how to put it together.

Self-described “Inventor Dad” [pepelepoisson]’s project is called Stecchino (English translation link here) and it’s an Arduino-based ... Stecchino uses an MPU-6050 gyro and accelerometer ...