David is doing a lot of great work with open source hardware telephony, check out the embedded Asterisk he’s working on… –
The IP04 is a Four Port Embedded IP PBX that runs Asterisk. The hardware design is 100% open. I just built the first IP04 prototype (really built, as in soldered), and would like to tell you about it. This post talks about the IP04 hardware, the bring up, an explosion (!), and compares the IP04 with the Digium Asterisk Appliance.
Curiously, hardware hacking is getting cheaper and easier. For example the tools for surface mount work are reasonably cheap (a soldering iron and stereo microscope), there is plenty of free CAD software, low cost PCB fabrication, and web based components stores like Digikey.
Building an Embedded Asterisk PBX Part 3 – Link.