Use APKPure App
Get Arduino Controller Bluetooth old version APK for Android
Use this app as a bluetooth remote controller for Arduino
If you want to control arduino via bluetooth for your project.
Let your android device be a remote control for any micro-controller with a bluetooth module.
Run the app, search for your bluetooth module and connect. Once you are connected you will be able to send your own commands to your arduino board using the keyboard or some fancy buttons. Send command with your voice.