I live in Lyon, France, which is a polluted urban city.
I got the idea to make a geolocated Sigfox powered sensor, that is able to monitor air quality anywhere, at any time.
It allows to build air quality heatmaps at street level, being able to tell where and when the pollution is accurately.
For instance, it is in beta tests in the city, gathering firsts data that helps to understand the pollution, and being able to take actions to reduce it.Hardware
I used Wisol 20 RCZ1 module, since it is a Sigfox (for autonomous data uploading), BLE (for smartphone connection), WiFi and GPS (both for geolocation).
I used a BME680 for Temperature, Humidity, Pressure and CO2.
And a Mics-5524 for gases.Firmware
The firmware is basically sending position (WiFi SSid's or GPS) and sensors values every 2 minutes if the object is moving (typically fixed on a air pollution mask, while cycling or walking).
It is also advertising in BLE while it is moving.Cloud
I used https://plugblocks.com to easily manage and visualize AirQule locations and sensors and users.
In fact, WiFi is preferred over GPS for geolocation since it consumes less power and it is faster to fix.