iPhone App to detect phone calls and alert Bluetooth module.

I need an app that "listens" for incoming calls and alerts an already connected bluetooth device. The App needs to work in "background" mode, that is when the app is not in the foreground, like a service. I need to have the full source code to be able to add to this App later on. I have some coding experience and have developed an app that can "catch" an incoming phone call and alert my BT module but it only works when the app is active (in the foreground). If you can provide a skeleton app that detects phone calls even when in background it could be sufficient for me to build on.