The architecture will need a central server: You report mouse location (within the DOM!) to this server and your peer will listen on these events. Ideally this should be part of blog server itself and a simple mechanism to allow your peers to subscribe to your events.
This also leads to extension of blog concept to a generalization of protocol for exchanging "What I am doing now" - in real time. For example the sites I am visiting just now, or research I am doing. The interested folks from the community can join together and produce a common blog as a result. (Such an interaction often tends to be more productive.)
Perhaps someone already has this implementation!