Well I downloaded the iBlacklist trial version last night and it looks pretty sweet.. You get a 10 day trial then have to purchase the App. Not all the functions work (duh) but enough to test out the app...
I will buy this for sure.
Oh and this is for a JB'd phone using iBlacklist downloaded via Cydia.
It's impossible to have such an app on an iPhone that's not jailbroken, because Apple doesn't allow apps to access the phone service, let alone access it while the app is not running.