Is there some reasonable means by which to detect activity in a circuit using a Raspberry Pi?
For example, say some device has a buzzer that goes off when it's done doing what it's doing and I want to detect this buzzer going off and then use software on the RasPi to send a text or an email. The software part I can handle but I have no clue how I would go about detecting the buzzer, I'm assuming there's a circuit inside the device that activates when the buzzer goes off and if I could physically locate this I could add some of my own hardware to the circuit for detection but I'm a software guy not an EE so I'm not really sure where to start.
Any ideas? Help would be greatly appreciated.