Any command by finger snapping.
・OS X El Capitan
・Python3
・numpy
・pyaudio
Run this command.
python mic.py
System audio volume is muted when you snap finger.
If you snap again, unmute volume.
Now, this can only control system volume. but, any command will running in future by finger snapping.
This need powerful finger snapping ;)
If you can't powerful finger snapping, I recommend to clap your hands :)