Airgradient's popular indoor air quality sensors are the first devices of their kind to be officially certified as "Works with Home Assistant". These open-source devices do not require an internet connection and enable local automation with air purifiers, air conditioners, or humidifiers and dehumidifiers.
To be fair, you can buy it as an “easy to assemble kit” for $138, which makes it very clear that you’re paying $92 for labor/calibration/certification.