A German company has developed software that makes the MacMini an IP PBX.
The software comes on an iPOD and works with the low priced MacMini. The entire system of software, iPOD and MacMini sells for under 3000 Euros.
This clearly goes into the VoIP game as something similar to Asterisk, but is not Open Source. Instead i look at this as a way to use one of the world's easiest computers in a very creative and useful way. Since the Mac OS is very, very stable, the reliability factors should be a very good starting point for buyers to think about.
This is similar to a Voxilla offering based on Communigate Pro.
The interesting point of distinction is how much less expensive Voxilla's system is. So you don't get the iPOD....