I remember xhtalk. It was a graphical X11 program which you configured with a list of hosts and usernames, and corresponding full names, and it ran “finger” at those hosts at regular intervals, looking for those usernames. If any of those usernames were seen to be logged in, they were shown in a list, and if you clicked on a user in that displayed list, a new terminal would be started with a talk session to that user. It was basically a precursor to the instant messenger craze, which had not yet started.