TrueCaller is a really excellent tool that is here to put an end to the activity of anonymous callers. What this new mobile app does is to gather the information on yellow- and white-pages from all over the world together, and (in the event the person who is calling you is not already on your contact list) let you know exactly who he/she is by looking there. So, the identity of virtually every caller will become known to you before you even answer. If the one who is tying to get to you is a salesperson or marketer, you will know about it all right away, ignore the call and have that number filtered out from then on.
And when it comes to your already-existing friends, then TrueCaller can look at their Facebook and LinkedIn profiles and see what they are currently doing. In that sense, TrueCaller is an app that can give context to any call you receive
Besides, TrueCaller can take care of updating your every phonebook contact and notify you when any friend of yours has changed his address.
TrueCaller.com In Their Own Words
Caller ID for your mobile with TrueCaller.
Why TrueCaller.com It Might Be A Killer
It is one of the best ways yet devised to avoid being annoyed by unscrupulous spammers – you will be able to individualize them, and filter their calls right away.
Some Questions About TrueCaller.com
How worldwide can this service eventually become? 
