I know I have a hard time keeping up with so many threads. I thought it would be nice for a user to send a quick invite for a certain member to reply. I don't have time to go through all my threads and don't like thinking a member could be waiting on a reply from me that I didn't see....So it would be a reply request function, maybe triggers a private message even.

Interesting idea. A forum with real-time alerts!

Not really within the scope of most forum designs. PM and chat seems to work best for those things, IMHO.