So Honeywell Home moved to Resideo a few years back and now Resideo bought First Alert and have a new app which is where you can run your Honeywell thermometers from. So the Honeywell Plug-In is sort of dead because it's all moving to First Alert by Resideo. You need to get an API key through First Alert by Resideo. Are there any plans for doing a PG3x plug-In for First Alert by Resideo? I would have put this topic in the Plug-Ins section but it's greyed out, I assume it's because it's getting consolidated with the rest of PG3 in this forum.

The app doesn't seem to connect to First Alert Smoke/CO2 detectors.

Haven't tried Thermostats yet.

Make sure you have the app that says “First Alert by Resido”. Also it looks like the only FA Smoke/CO2 are their SC5 smart line, which makes sense.

My recent unsuccessful attempts are documented here

Note that the First Alert app is going to be replaced by the Resideo Connect app. That will be the 4th name/app change so far.

I'm curious where you heard about this "Resideo Connect app"? I've searched all over for an app with this name and can't find any reference to it. The latest I see is Resideo urging people to move to “First Alert by Resido”. If fact, when I called their tech support, “First Alert by Resido” is the one they told me to signup for an account to get API code.