Just connect to BT-PAN NAP and die

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="net.m2hq.pannacotta">

    <uses-permission android:name="android.permission.BLUETOOTH" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.AppCompat.Translucent">
        <activity
            android:name=".MainActivity"
            android:launchMode="singleTop"
            android:noHistory="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

MainActivity.kt

package net.m2hq.pannacotta

import android.annotation.SuppressLint
import android.bluetooth.BluetoothAdapter
import android.bluetooth.BluetoothClass
import android.bluetooth.BluetoothDevice
import android.bluetooth.BluetoothProfile
import android.bluetooth.BluetoothProfile.ServiceListener
import android.content.Context
import android.os.Bundle
import android.os.Handler
import android.util.Log
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import java.lang.reflect.Method

class MainActivity : AppCompatActivity() {

    companion object {
        const val MY_TAG = "MainActivity"
    }

    var mBTPanConnect: Method? = null
    var mBTSrvInstance: Any? = null

    var isConnected = false

    @SuppressLint("PrivateApi", "DiscouragedPrivateApi")
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        if (BluetoothAdapter.getDefaultAdapter()?.isEnabled == false) {
            Toast.makeText(applicationContext, "Bluetooth is not enabled", Toast.LENGTH_SHORT).show()
            finishAndRemoveTask()
            return
        }

        // ref: https://stackoverflow.com/questions/22864670/enable-bluetooth-tethering-android-programmatically
        val classBluetoothPan = Class.forName("android.bluetooth.BluetoothPan")
        mBTPanConnect = classBluetoothPan.getDeclaredMethod(
            "connect",
            BluetoothDevice::class.java
        )

        val btPanConstructor = classBluetoothPan.getDeclaredConstructor(
            Context::class.java,
            BluetoothProfile.ServiceListener::class.java
        )
        btPanConstructor.isAccessible = true

        mBTSrvInstance = btPanConstructor.newInstance(applicationContext, BTPanServiceListener(applicationContext))
    }

    override fun onDestroy() {
        super.onDestroy()
        Log.d(MY_TAG, "onDestroy")
        Handler().postDelayed({
            android.os.Process.killProcess(android.os.Process.myPid());
        }, 3000)
    }

    inner class BTPanServiceListener(private val context: Context) : ServiceListener {

        override fun onServiceConnected(
            profile: Int,
            proxy: BluetoothProfile
        ) {
            Log.d(MY_TAG,"onServiceConnected")

            if (isConnected) {
                // to run once
                return
            }

            val bluetoothAdapter = BluetoothAdapter.getDefaultAdapter()
            if (bluetoothAdapter?.isEnabled == false) {
                return
            }

            val bondedDevices = bluetoothAdapter.bondedDevices

            bondedDevices.forEach { device ->
                val btClass = device.bluetoothClass
                if (btClass.hasService(BluetoothClass.Service.NETWORKING) &&
                    btClass.hasService(BluetoothClass.Service.TELEPHONY) &&
                    btClass.deviceClass == BluetoothClass.Device.PHONE_SMART) {

                    Log.d(MY_TAG, String.format("Name:%s, Class(Service/Device):0x%s", device.name, btClass.toString()))

                    val success = mBTPanConnect?.invoke(mBTSrvInstance, device) as Boolean
                    if (success) {
                        Toast.makeText(applicationContext, "Connecting to " + device.name, Toast.LENGTH_SHORT).show()
                        isConnected = true
                    } else {
                        Toast.makeText(applicationContext, "Something wrong with connecting to " + device.name + " (maybe already connected?)", Toast.LENGTH_SHORT).show()
                    }
                }
            }

            finishAndRemoveTask()
        }

        override fun onServiceDisconnected(profile: Int) {
            Log.d(MY_TAG,"onServiceDisconnected")
        }
    }
}