Addon for CMS comment notifications?

[vexxy]

So I'm looking for some kind of mod/addon that enables CMS comment notifications. Like a thread/post notification works, if an user is subscribed to a thread, he will receive an email/pm notification that he thread has been updated. I would love the same thing on comments, since if an user comments, there's a very slim chance that he'll come back to that article.

I've looked around the site, used the search etc..didn't find anything. Maybe I'm missing something.