How to create Background Services in iPhone like Android?

I want to create a function which work in background in iPhone. I want to set Notification for any change in NSUSerDefault Value. I saw many Serv开发者_运维问答ices running in Background of Android. How can I Make background Service this in iPhone of some application ??

iOS apps are only allowed to run in the background for a few well-defined reasons, such as implementing VoIP and playing audio. Monitoring preferences isn't one of the permitted reasons. That's okay, though, because each app runs in its own sandbox and is unable to affect the environments of other apps, and other app will be able to change your app's preferences.