The Best Caller ID Cydia tweak, developed by Bozydar Slavik, allows you to instantly know who is calling before you pickup. Best Caller ID acts as a spam blocker, and you never have to pickup unwanted calls again. Even searching for any phone number becomes easy with Best Caller ID. You are able to find business, financial, friends or family phone numbers. Get in touch with people you may know.
Note: There will be an app added to the home screen.
Best Caller ID is a commercial package (3-days free trail; $1.80 /month subscription) and is available from the BigBoss repository. If you end up trying this tweak let us know what you think of it in the comments.