This project is code for a smart ring that accepts different gestures. When an appropriate gesture is performed, it sends a bluetooth signal to an app, where the app can play/pause music and also change the volume.
Arduino code is based off the Krodal Arduino MPU-6050 code and this HC-05 arduino example
Android app is based off Mayoogh/Arduino-Bluetooth-Basic
Here's my YouTube video demonstrating the smart ring