Trigger event by selfistick (phone jack)

I want to trigger an event by pressing the triggerbutton of a selfiestick.
Its the same as if I hit decrease or increase volume on a headphone connected to a phone.
Both selfistick and earphones with volumecontrol are generally connected by a standard phone jack (4 pins).

Both ways are generally detected by android or iphones standard photo apps to shoot a photo for example.

My question is, if we can detect the signal coming from the phonejack to trigger custom events.
Any way?