You know about True Caller, right ? That cool app which allows you to look up phone numbers from anywhere in the world, is on Windows Phone 7. You can search for a number and the app returns the name and address(when available) as results. You can search international numbers as well by changing your country.
The app is about to get even more awesome. Bringing it on par with its counterparts on other platforms, it will soon add the realtime caller ID feature. We contacted the devs, and they told us with Mango, it will be possible to access the contacts API and add realtime functionality to the app.
[Source]