CallerUtility is a free Windows Mobile application for looking up unknown callers (phone numbers which are not listed in your Address Book) for incoming and outgoing calls as well as unidentified SMS senders on your mobile device. When there is a phone call from an unknown caller, the program looks up one or more databases and displays the information on top of the incoming call dialog box.

Key features of CallerUtility for Windows Mobile devices include:

+ Automatically lookup unknown callers based on incoming caller ID
+ Manually lookup unknown SMS senders
+ Manually lookup unknown outgoing calls
+ Checks if a call is from a telemarketing company
+ AppToDate integration

There are different versions of the application based on country location including one for United States. Other versions can be downloaded from the CallerUtility thread at XDA-Developers forum.