I had been looking for software like this since I got my Pearl the day it came out - I tried BerryBlocker and the software would never work and the support team stopped responding. They also have not updated in some time.

I recently bought Black & Whitelist and love it. The developer was a great help with an issue I had with it (I enter my phone entries with spaces) and was able to fix the problem and release a new version a few days later. He is also planning on adding some features soon.

My reco is Black & Whitelist.