I built this device for someone to use in their home in California, where seasonal wildfires and other allergens are a frequent concern, and where microclimates make local sensing uncommonly useful.
It's a RasPi Zero W that talks over i2c to a Teensy that interfaces with two identical air quality sensors, Honeywell units that are also visible in the PurpleAir hardware that I was trying to best.
The eink display shows a timeseries graph of the last ~3 hours of local data, along with forecast information for the region as supplied by the Open Weather API.

How disappointing - this site used to have an easy-to-fill out BOM and repo area, but that's gone. I guess I'll document this on my own website instead.