A major factor in telepresence immersion is eye-contact. http://www.google.com/search?q=telepresence+eye+contact Perhaps someday a YC company will figure out how to inexpensively enable eye-contact over ordinary video chat (teleconferencing).
That's the half-silvered mirror solution (for full eye-contact teleconferencing). I was thinking of the other solution: the software-based one that corrects the images in terms of pupil-direction.
That could get really creepy, really fast..
It seems to be what HP and Cisco are using for their immersive telepresence systems. I have seen plenty of rave reviews of Halo, and never any complaints.