One of these days I'm going to have to rig up something to start the house fan when the CO2 goes above 800 ppm and I think you'd need a different sensor with a realtime output port for something like that.
Direct feedback is cool, but a simple schedule is really easy & reliable. Even occupancy detection isn't all that critical- nobody wants to come home to a stuffy house, and most people's schedules are very predictable.
These days IoT is so widespread that something like a $25 WeMo smart outlet is hard to beat. Hard wired is "best" but a million times more hassle and more expensive.
One of these days I'm going to have to rig up something to start the house fan when the CO2 goes above 800 ppm and I think you'd need a different sensor with a realtime output port for something like that.