Re: Upvoted for McGyver like innovation...
SheevaPlug was a cheap ARM based server that fitted inside its own wall wart. They were $99 in 2009. These days, a Pi would be cheaper, but not as tidy as it requires an external wall wart. The computing requirements are not that steep, but as this is a 24x7 widget you might want something from this decade to save power.
Asterisk is a free software router. The good news is it does everything. The bad news is you are going to have to read the manual to set it up. I liked the idea too, and my first thought was, why not put asterisk in the router. A quick web search later, and I discovered this was old news in 2010.
