I have three of them. The real issue is that they are not interlinked. If one goes off, the others do not. Not totally useful if there is an overnight fire in the basement and the people on the 2nd floor can’t hear the smoke alarm. I was hoping there would be a means to fire the others from the ST automation, but I have not been able to do that. I am considering removing them and going back to hard-wired interlinked alarms because safety is much more important than getting notifications on my phone.
You can always add an Ecolink Firefighter to listen for the alarm from your hardwired detectors and get alerts. That’s what I intend to do next time I find myself with some cash to spend on HA upgrades.