registerReceiver(this.screenOnListener, new IntentFilter("android.intent.action.SCREEN_ON"));
registerReceiver(this.screenOffListener, new IntentFilter("android.intent.action.SCREEN_OFF"));

https://stackoverflow.com/questions/10402686/how-to-have-led-light-notification

public class ScreenOffListener extends BroadcastReceiver
{
    public ScreenOffListener() {}

    public void onReceive(Context paramContext, Intent paramIntent)
    {
        Notification notif = new Notification();
        notif.ledARGB = "0xFFFF0000"; // Red
        notif.flags = Notification.FLAG_SHOW_LIGHTS;
        notif.ledOnMS = 200; 
        notif.ledOffMS = 200; 
        nm.notify(NOTIFICATION_ID, notif);
    }
}

public class ScreenOnListener extends BroadcastReceiver
{
    public ScreenOnListener() {}

    public void onReceive(Context paramContext, Intent paramIntent)
    {
        NotificationTest.nm.cancel(NOTIFICATION_ID);
    }
}