iOS display notification based on incoming phone call

Question

Is it possible to have a background app display a notification based on who is contact details from an incoming caller, either before the call is answered or during?

Answer 1

No, the system will not allow you to interact with phone calls in any way.

Answer 2

You can set the image for certain people in the address book using the Address Book API. That way, a certain background image (potentially with a textual message) will be shown, based on who is calling.

Answer 3

With time, things change. Look at sync.me, when you get an incoming call, the latest post on facebook will show just above the accept/decline button. Though I still can't get the idea of how it is done.