Well dude, this is not possible in IOS, because apple has given only few application capabilities to run the app in background. Incase if you want to perform any action when user kills the app, it is impossible. You will be notified only the app termination action in AppDelegate class. read more
But iOS Human Interface Guideline for Starting And Stopping App, suggesting that Never use Quit or Close button to terminate Application. Rather then that they are suggesting to display proper message to explain situation. An iOS app never displays a Close or Quit option. read more