An area where users of the system can chat in realtime
If it's not too hard maybe even make it so you can chat with users on the system privately and you can decide who.
I got the idea from my own office. I was home and my office manager at the office. I couldn't talk but needed a way to chat with her. Hell my fingers.
eyeOS has this kind of thing built in. Worth looking at to get the idea of what I'm saying if not understood.