A widget over the state the app already has

Android only. The widget is not a second app. It is a second renderer of the same state, and it gets there by being a dependency-injection component itself:

// adapted — the widget itself is a dependency-injection component
class MainAppWidget : GlanceAppWidget(), DiComponent {
    val playerStateHolder: PlayerStateHolder by inject()
    val serviceScope: CoroutineScope by inject(named(SERVICE_SCOPE))
    …
}

class AppWidgetReceiver : GlanceAppWidgetReceiver() {          // the receiver is a one-liner
    override val glanceAppWidget: GlanceAppWidget = MainAppWidget()
}

Two consequences worth being explicit about: