What I would like to do is mimic how Wordpress shows an administrator how many new updates there are for installed plugins (a tiny number displayed next to a link). The main difference is that I want to serve this info to a logged-in user on the front end (since they last visited):
- new messages they've received (Buddypress)
- new forum posts (Buddypress)
- new posts for "favorited" categories
Not sure where to find the code that provides plugin update notices but that would be a start...