switchaudio-osx 0.0.1-unofficial (new formula)

This formula provides the OS X command line utility
SwitchAudioSource. Users will be able to switch audio sources
(input/output/system) using the command line and without needing
a GUI tool. It works with 10.7 Lion, 10.8 Mountain Lion, and 10.9
Mavericks.
Just inline this variable.