If you set the WABAC machine back a few years we can get to what is likely the smallest DIY Asterisk appliance ever undertaken, based upon the appropriately name little Gumstix family of boards. To my knowledge Kristian Kielhofner of Astlinux and Star2Star fame was the first to port Asterisk to these teeny little boards. He showed it at Astricon in 2005.
At the time featuring a 400 MHz Xscale processor the wee Gumstix may not be the least powerful host ever selected for use with Asterisk, but measuring only 20 x 80 mm it surely must be the smallest.
Despite it’s small size the board was surprisingly powerful, especially if not pressed hard for floating point operations. Kristian’s port of Asterisk was very experimental. I don’t believe that it ever reach a release candidate.
Nonetheless, the concept of Asterisk on Gumstix ignited a lot of ideas about embedding Asterisk into other devices. For example, you could embed an Asterisk system into an existing SIP desk phone without requiring the complicity of the manufacturer. In so doing you would have the ability to give the phone sophisticated internal dial plan capability with support for multiple accounts and protocols.
Even just embedding a SIP-to-IAX2 protocol translator would provide a definitive NAT traversal solution without resorting to using cheap Chinese IAX2 phones. The ability to run effectively run IAX2 on a premium SIP desk phone would certainly be handy for anyone with an Asterisk or Freeswitch based back-end and remote home office workers.
Over time Gumstix have evolved to use ever fast processors, and offer a wide range of interface boards. They’ve become wildly popular with the amateur robotics crowd.
The one issue for this hardware is the lack of readily available cases.The various CPU and interface boards clip together in a fashion that, while not unattractive, isn’t physically robust. To be used beyond experimental applications they should be securely mounted into another device or a some kind of case.