Apple Watch Ammeter allows you to turn your Apple Watch or any watch with a magnetometer into a device that can measure DC currents. With the magnetometer found in Apple Watches newer than Series 5, this demonstration uses a coil of wire wrapped around the watch to manipulate the magnetic field sensed. By calculating the magnetic field generated by the coil, a 5-turn coil around a watch with a 48 mm diameter can show current changes of about 10 mA. While the magnetometer may not be perfectly centered in the coil, an app like ‘Sensor-App’ can be used for calibration and to display current in Amperes. This innovative setup allows for detecting DC currents, but not AC currents like household power. The Earth’s background magnetic field and careful readings enable detection of subtle changes in current with a simple setup.
https://github.com/jp3141/AppleWatchAmmeter