The Unity3D I-Room tests now include VoIP. The main window is a Unity3D build of the I-Room in an open terrain. This is delivered using the SmartFox MMO server. Around the 3D view are a number of widgets to provide a Twitter feed on a nominated #tag, a shared whiteboard/presentation facilility vased on Dabbleboard, and now a Flash-based video-teleconferencing facility from Tokbox.
The demonstration I-Room with VoIP is avaialble at: http://www.aiai.ed.ac.uk/~ai/unity/iroom-mmo/iroom-voip.html but please note that the SmartFox server required for MMO access is not always kept running.