One really important bit of information to add to the first full paragraph is that when the app tries to use startMonitoringForSignificantChanges: for the first time, the user is asked whether or not they want the app to. If they select "Don't Allow", then it's game over for that app until the user changes the setting in Settings. This doesn't stop iOS from doing what it's doing, but should quell fears that random apps are just logging all kinds of user data and sending it to who knows where.