Tombstoning is something the WP8 operating system does automatically. All it does is terminate your app that’s been suspended in the background too long or if the OS want more memory for the currently running app. You should handle this situation much like how you would do it on iOS, as in you should save your app’s current state to file when your receive an “applicationSuspend” system event in Lua. And like iOS and Android, you can’t fully depend on the “applicationExit” system event from being dispatched for when the OS forcefully terminates the app (ex: kind of like a ctrl-alt-delete equivalent on Windows). The “applicationExit” happens when the end-user gracefully closes the app.