Sentinel was just published to Cydia and is a call blocking extension for iOSdevices. 

Sentinel adds to Apple’s current call blocking feature so that you can view a history of the blocked numbers that have tried to call you, when they tried to call you and how many times they were blocked.

In the settings you can have Sentinel show optional banner and alerts notifications when a call is blocked and also enables you to block callers with an unknown number.

This tweak is a must if you are curious about the people you have blocked and is a bargain at 99c. 

You can download Sentinel from the BigBoss repo.