more difficult than you may first think.

first you need to think about the information/commands that are going to be used to express what you want. Is the viewer on another machine going to be a view onto the other program? is it going to be the same program but run in a slave mode?

I'm not familiar with the multicase/map demos.

I would suggest fat client over thin - meaning that any maps you want to share need to already be installed on "viewers'" machines. you would then communicate via sending coords and scale through a socket.