Kidde smoke alarm interconnect sensor
I made this when I first had Wink, moved it over to SmartThings, and now have it in Home Assistant.
Kidde SM120X Interconnect Accessories Smoke Relay Module https://a.co/hov76Yx
I would imagine there is a first alert version also.
Door/window sensor of your choice
Mine is a Go-control and I have had this setup since I started with Wink in 2016. At the time they didn’t see the external contacts so I removed the reed switch and Soldered wires to the pads.
Drywall box to put the relay in
Blank wall plate to install sensor on
Some wires to connect relay to smoke alarm wires
I added an up close of the relay module as it has the wiring printed on it.
Caution the smoke alarm beeps in this video