My project idea is to attach "something" to my Intercom and when it receives an electric signal (someone rings the door bell), contact a local web service in a home server and that server sends a push notification to phones.
The part of the project I currently control is the one of the server and the push notification (I'm developer), the part I'm lost is the hardware part.
It seems the ESP8266 looks like a good option for me. But, I need to know how to make it react to the ring signal, and how to make it being powered with the Intercom power source, can you give me some advice?
Maybe the SparkFun ESP8266 can be a better option?
Based on Chris Stratton comments, Will it be a better way to have a ESP8266 with is own power supply and track the acustic signal of the Intercom rather than use the internal electric of the Intercom?
If yes, what I need to make my device track the acustic signal?, and, is there any battery source that informs about power life duration? Or the life of the battery is long enough to not worry about it?
Continuing with my initial idea I found this Current Sensor Module ACS712. I understand that this could "bypass" the cable that comes from the portal to the Intercom and that causes the intercom to ring so that when this cable receives power (someone called), could I detect that change?
It seems to me a more precise and simple option than the acoustic detection.