How to get notifications when the headphones are plugged in/out? Mac

I'd like to get notified when headphones are plugged in or out in the headphone jack.
I've searched around for this on stackoverflow but I can't seem to find what I'm looking for for the Mac, I can only find for iOS.
So, do you have any ideas on how to perform this? What I want to do with this is: when headphones are plugged out I want to programmatically pause iTunes (iOS-like feature).
Thank you!