Felipe Cecagno, a member of the GT-Mconf team working in the Laboratory of Prav (located in the Institute of Informatics, Federal University of Rio Grande do Sul, Brazil) posted this message to bigbluebutton-dev giving an update on their progress to create an Android client for BigBlueButton.
Progress is good. They posted this YouTube Video showing a working prototype (chat is now implemented).
Their project is open source:
With an Android client now in play, could an iPhone client be far behind?