I'd like to monitor the ambient sound with my Mac, and run a script to do a few things when the input sound volume reaches certain level. I don't intend to record or recognize sound, I just want the computer to do something such as sending SMS or turn on the light through USB peripherals when the phone rings, the baby cries, or the dog barks, etc. It's part of a home-automation research project.
I have a mic plugged in the line-in, and I can see the sound volume changes in the sound perference panel. But I don't know how to catch the current input sound volume. I'd searched Google with every keywords I can think, but found nothing.
Any hint would be grateful.