Although the question above might be old I want to inform you that there is now such an App available in the App Store. It can even look up unknown numbers in the web (reverse caller id lookup) and then tells you who's calling. The App is called:

RiggRing - Who's calling me from this number?

Available on the App Store.

Regards

Gabe

There is now such an App available in the App Store. It can even look up unknown numbers in the web (reverse Caller ID lookup) and then tells you who's calling. The App is called:

RingRing - Who's calling me from this number?