How Inbound VoIP Calls Could Happen on the iPhone
Imagine if you will, a VoIP service hooked into Apple’s Push Notification Service (APNS). An inbound call comes in on your VoIP service. The notification is pushed to your handset. From that notification, you can launch a VoIP app that essentially connects the incoming call to your iPhone or iPod Touch over WiFi.
While not perfect, this is basically a way around the whole lack of background applications on the iPhone. Any service provider could easily do this.
There are some logistics to work out with this system, such as what happens if APNS is delayed in delivering the message or the caller gets impatient and hangs up, but none of those problems are insurmountable.
So the question is: which service is going to implement this first?