Sorry but right now it really can’t be done..
On iOS 5 there isn’t any access to call_history.db -> Which is exactly what you were looking for.
The app mentioned here:
http://itunes.apple.com/us/app/callog/id327883585?mt=8
Does not work with iOS 5 (don’t download but check the users’ reviews..)
On iOS 4, you might still be able to get away with it:
But who develops solely for iOS 4 these days..?