Built-in camera app is locked after a timeout (lock screen timeout). Original (NativeFilterDemo) app is not locked also.

480, 853 are quite correct values. It's for 720p devices (1280x720 resolution). For other devices it should be 480,800. So it's okay

You should find another way to show it fullscreen without rebuilding the visual tree. Try hiding all other controls. When you remove map control...

WriteableBitmap or Canvas is the way to go. Depends on required performance. Pen/Brush/Geometries can be replaces with Canvas +...

There is a very simple way to do what you want - if xap contains file WMAppPRHeader.xml (check using Application.GetResourceStream ), then it's app...