I had a dream last night that I was using heyuri last night. In this dream, there existed a special feature. You could invite another user to participate. There were two panes. On the top, there was a live chat to communicate with the other person, and below, was the shared window. This is where the activity took place. In my dream, it was programming; but I suppose it could be anything else with text, or even drawing.

It could be competitive or cooperative. I suppose in the competitive mode it might be a good idea to have two separate windows for each user and not one that both can edit. I believe also in my dream that others could view it and post to the chat but not edit the shared window.