I would like to integrate my Nest Protect with a Arduino/Konnected/RPI/etc that can communicate with SmartThings/Hubitat. I took one of my Nest Protects apart (battery version) to determine the ideal method for physical integration.
Just in case others are reading this, I should mention that this will only work with the US format nest protects, it’s listening for a very specific audio pattern. It won’t work with nest protects or other smoke sensors in England as different countries have different smoke sensor audio patterns.
I was able to integrate this with ST using a NodeMCU (on Konnected) by simply connecting the terminals going from the Nest Protect’s siren to the ESP8226 board. I had to disable the internal pullup resistor on the Konnected board.