client to client communications

[Ego]

I'm thinking about writing a simple status monitor addon and was wondering
what techniques are available for sending update information about a status
to another client. What have people done? What works?

The status would not be an in-game value, it would be custom for the
addon. Probably have a simple display on the client side, but what I want
is for the user to select a value, and for other clients to have the ability
to see that value.

The data would likely be small (a simple string or number) so any method
of sharing data would likely work.