Proving that there is a lot of horsepower in the Raspberry Pi, a proof-of-concept has been developed that uses the Raspi as a guitar effects processor. Among the steps taken to get low latency with the audio interface. the Pi is running headless with more RAM allocated to the CPU.
Alex Ruiz has created a solution that was prototyped using a RPi and an off-the-shelf Analogue Telephone Adapter and it works great. Being an independent coder, the advantages the RPi presented as a development platform both in cost and flexibility made it an obvious choice for writing experimental phone software. Because of the low cost, he was able to successfully fund the development and beta distribution of units on his own. This helps enormously, as he can now claim that his solution is not theoretical and that it is working in a real business environment.