Just a thought.
I have been trying something on the same lines using Netmeeting. Instead of "popping up" a new window, we have tried using a Netmeeting interface embedded into an HTML document. This allows me to "share" applications, including my browser. However, bandwidth, and the 8 client limitation associated with Netmeeting, have caused some heartache.
I would love to see something supporting a more synchronous learning environment. Moodle is great for asynchronous learning, but could really use a boost like this for synchronous communication. Don't get me wrong, the chat module is great for now, but looking down the road this would be awesome.