Notification for No Post in X Days by Forum

[Forensic]

I could use a notification system that will notify a group or the individual Forum Moderators if a post has not been made in their section within the last X number of days.

We have a few sections that we offer to people as long as they stay active. I'd like to send them a PM and/or email to remind them that they are slacking.

Has this been done? I didn't see it in a search but considering the terms notification, post, days are all pretty generic.