Itty-bitty Android root-only app that activates permanent Bluetooth discovery

The basic concept is that you need to call BluetoothAdapter.setScanMode with the correct arguments. It is a private method, so reflection is required. Furthermore, the permission required to call this method is WRITE_SECURE_SETTINGS, so the application MUST be installed in /system and it must be signed.

Once you build the app you can sign it with some key (it doesn't really matter what, could be self-signed) jarsigner -verbose -keystore my-release-key.keystore AlwaysDiscoverable/bin/AlwaysDiscoverable.apk mykeyname

I have included a copy which I signed with a dummy key in the repo.

Kill the task to stop it from being discoverable