You have to have asked for the Significant Location Update Service.
I have verified this in code numerous times, and Apple representatives have confirmed in the development forums.
I have verified this in code numerous times, and Apple representatives have confirmed in the development forums.
The focus of this article was location-based apps, but there are also interesting behaviors with voip and audio applications.
http://developer.apple.com/library/ios/#documentation/CoreLo...
is the place to start, where they state "If you start this service and your application is subsequently terminated, the system automatically relaunches the application into the background if a new event arrives."
The other required piece of information is that when you reboot the phone, it triggers this event for all applications that have registered this service.
More info at: https://devforums.apple.com/message/307725
If you're further interested, downloading the SongMap sample code from Apple will let you test this functionality yourself.