This proof-of-concept app demonstrates to ability to turn on and off the built-in Arduino LED over Bluetooth.
You must have your Android device paired with the Arduino from within settings before this app will operate.

I also provide this app in a Kodular project file on my website for you to tinker with and modify it at will.

For more information please read the detailed guide on how to use this app here:
https://installtekz.com/bluetooth-arduino-led-android-free-kodular-app/