I recently replaced the smoke detectors in my house. I wanted to get ones I could get status from, but none of them that I found (like the First Alert ZCOMBO) would also work with the interconnect. I definitely wanted less infrastructure between one detecting smoke and them all going off.
So I went with regular detectors (Kidde PI2010) that are hardwired A/C, battery backup, dual sensor and interconnected. $30 each. I already have new, separate CO detectors from when we replaced the furnace a few years ago.
To tie an alert into Hubitat, I picked up a Ecolink Z-Wave Plus Firefighter FF-ZWAVE5, which you mount next to the smoke detectors and a microphone picks up the alarm.
I would have gone with the Kidde SM120X relay, except I couldn't find another access point to the interconnect wire anywhere in my house outside of the attic. I would have had to tap into the wire in the attic and put it up there, and I didn't want to do that.
