Does anyone have any idea how I could get smarthings/google home/ecobee to trigger when my Aranet4 hits a certain CO2 level? I’ve no idea how to even start.
Aranet only offers integrations using Bluetooth, so unfortunately it cannot be directly integrated with ecobee or smartthings.
Some models of Homey pro do have an available integration for it, but that’s a whole different hub, and does not itself have a SmartThings integration.
There is also an integration with home assistant as long as you have added a Bluetooth radio module to your home assistant setup, and it would probably be easier to create an integration between that and smartthings. But “easier“ doesn’t mean “easy“ – – it just means possibly doable.
You can read more about the possibilities in the aranet forum. Just remember that no matter what code you write, that still doesn’t get the Bluetooth signals into smartthings, so you’re going to need an intermediate device for that purpose. 