I used TeamViewer to test in a classroom setting in order for teachers to collaborate without leaving their rooms. We did a beta test which included 2 different site locations, 6 teachers, 2 parents, 1 desktop running WIN OS, 1 desktop running MAC OS, 1 iPhone, and 1 iPad. Everyone was able to participate in the "meeting". There is even an option to just call in, i.e. only use the audio module to join. In addition, we tested TeamViewer as a remote assistance software. READ INSTRUCTIONS! This was the part you really have to know what you are doing.