@lee , some day I would like to add outside intakes and automated dampers that let me blow outside air into the house when the outside temp is in the Ecobee set zone (maybe a little tighter band). I would probably try to do it using Home Assistant with Node Red since I’m already using Home Assistant with Sense, NuVent, and Ecobee integrations.
I don’t include AQI, but I have created some performance monitoring for my 2 HVAC systems. My main goal was to track when heating or cooling show degradation vs past performance, but looking at temperatures in the registers closest to my two air handlers.
More on what I can see here, but the main thing is that I can see how far those registers drop when the cooling comes on, and how warm they go when the furnace is on. Plus the electrical energy expended.