grep is your friend.
Has it been developed yet?
I developed a post approval plugin, but it currently requires manual changes to the core code in order to function. If you're feeling adventurous, you can download it here, instructions are included:
I think I might have a way to get it working without the changes, but I have yet to experiment with that.
Go figure, that was easy.
A new version will be available in just a minute that requires no manual changes.
There, new version is up, provides a pretty robust post approval system. Not a lot of fancy features yet and there aren't any config options, but it will work. Let me know how the new version performs, I didn't have time to do bug testing yet.