Looking for advice on compatible hardware

Hi guys, I’m currently working on renovating a house and I’m looking to outfit a few things to setup some basic automation. I picked up some sonoff switches and am going to flash the firmware to make them openHAB compatible. I’m also looking to buy a number of hardwired fire detectors and was hoping for some suggestions of cheap units that are compatible with openHAB as I believe I have 6 fire alarms to install. Any help or suggestions are appreciated.