it is known as CosmoPBX. You can get it and more information at: http://cosmopbx.sourceforge.net/. You must be forewarned though that it is NOT SECURE, so do not use it in a production environment. In any case, a great tool for experimentation with use on an intranet or private network. With wifi access to your network, voip applications for your touchpads (android and etc) should connect to it fine.
For our purposes, we booted it in a virtual machine. You can use a web browser to connect to the server remotely to configure any settings. ( i.e.: http://192.168.1.101:8088) Then you can connect with your favorite voice applications. In our case we used Ekiga from a desktop Linux workstation. Just a matter of setting up Ekiga with the ipaddress of the voip server and you are in business. When we connected to the server, it automatically answered and gave us a voice greeting and instructed us how to proceed.
The advantage of the live cd is that you can get familiar with voip, sip, and all that is involved before you invest in a pbx system for your office and or home. If you wanted something more permanent, you could try FreePBX, (http://www.freepbx.org) but it has to be installed. Though the traditional phone lines are becoming extinct, you can get a special card for your computer to allow the server to connect to an old fashion phone line.
Other accessories you might consider are ip to analog converters so that you can use existing old fashioned analog phones as part of the network. Lately it seems as though they may have jumped up in price. We bought a couple on closeout at Fry's a few years back. You also have to be careful as they are usually configured for a commercial "pay for" network. We bought a couple, but used available third party software to convert the units to work with our voip server.
As well as server, you can access the analog to ip converters via a web interface. That means you do not have to use sneaker support to set them up or disable them if need be. Barely touched the surface of voip, so I encourage to try it. If you get a chance,. they make a great home intercom system.