Jetpack Compose OverlayService. You have to have all the correct permissions granted and in your manifest, but if you do, this this will show a green box with "Hello" in it!

MyLifecycleOwner.kt

import android.os.Bundle
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleRegistry
import androidx.savedstate.SavedStateRegistry
import androidx.savedstate.SavedStateRegistryController
import androidx.savedstate.SavedStateRegistryOwner

internal class MyLifecycleOwner : SavedStateRegistryOwner {
    private var mLifecycleRegistry: LifecycleRegistry = LifecycleRegistry(this)
    private var mSavedStateRegistryController: SavedStateRegistryController = SavedStateRegistryController.create(this)

    /**
     * @return True if the Lifecycle has been initialized.
     */
    val isInitialized: Boolean
        get() = true

    override fun getLifecycle(): Lifecycle {
        return mLifecycleRegistry
    }

    fun setCurrentState(state: Lifecycle.State) {
        mLifecycleRegistry.currentState = state
    }

    fun handleLifecycleEvent(event: Lifecycle.Event) {
        mLifecycleRegistry.handleLifecycleEvent(event)
    }

    override fun getSavedStateRegistry(): SavedStateRegistry {
        return mSavedStateRegistryController.savedStateRegistry
    }

    fun performRestore(savedState: Bundle?) {
        mSavedStateRegistryController.performRestore(savedState)
    }

    fun performSave(outBundle: Bundle) {
        mSavedStateRegistryController.performSave(outBundle)
    }
}

OverlayService.kt

import android.app.AlertDialog
import android.app.Service
import android.content.Intent
import android.graphics.PixelFormat
import android.os.Build
import android.os.IBinder
import android.util.TypedValue
import android.view.Window
import android.view.WindowManager
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.wrapContentSize
import androidx.compose.material.Text
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.platform.ComposeView
import androidx.compose.ui.unit.sp
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.ViewModelStore
import androidx.lifecycle.ViewTreeLifecycleOwner
import androidx.lifecycle.ViewTreeViewModelStoreOwner
import androidx.savedstate.ViewTreeSavedStateRegistryOwner
import com.viatek.fitnation.echelon_android.R


class OverlayService : Service() {

    val windowManager get() = getSystemService(WINDOW_SERVICE) as WindowManager

    override fun onCreate() {
        super.onCreate()
        setTheme(R.style.ThemeOverlay_AppCompat_Light)
        showOverlay()
    }

    private fun showOverlay() {
        val layoutFlag: Int = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY
        } else {
            WindowManager.LayoutParams.TYPE_PHONE
        }

        val params = WindowManager.LayoutParams(
            WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.WRAP_CONTENT,
            layoutFlag,
            WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE or WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN or WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
            PixelFormat.TRANSLUCENT
        )

        val composeView = ComposeView(this)
        composeView.setContent {
            Text(
                text = "Hello",
                color = Color.Black,
                fontSize = 50.sp,
                modifier = Modifier
                    .wrapContentSize()
                    .background(Color.Green)
            )
        }

        // Trick The ComposeView into thinking we are tracking lifecycle
        val viewModelStore = ViewModelStore()
        val lifecycleOwner = MyLifecycleOwner()
        lifecycleOwner.performRestore(null)
        lifecycleOwner.handleLifecycleEvent(Lifecycle.Event.ON_CREATE)
        ViewTreeLifecycleOwner.set(composeView, lifecycleOwner)
        ViewTreeViewModelStoreOwner.set(composeView) { viewModelStore }
        ViewTreeSavedStateRegistryOwner.set(composeView, lifecycleOwner)

        windowManager.addView(composeView, params)
    }

    override fun onBind(intent: Intent): IBinder? {
        return null
    }
}