When closing the SimpleAR application in the emulator by using the Back button, I get a NullReferenceException when calling ARDisplay.StopServices();
 
protected override void OnNavigatedFrom(System.Windows.Navigation.NavigationEventArgs e)

    {
        // Stop AR services

  ARDisplay.StopServices();

 

        base.OnNavigatedFrom(e);
    }

 
On my Samsung Focus, after running SimpleAR, the compass seems to lock itself to a particular direction and won't vary more than a couple degrees from that direction to either side. A hard reboot of the phone will reset the compass in the SimpleAR app.