This document discusses citizen sensing and monitoring of environments. It presents several projects that allow citizens to monitor air quality including the London Air mobile app, environmental monitoring Arduino kits, and air quality monitoring devices attached to street sweepers, robotic dogs, pigeons, and eggs. The goal is to experiment with environmental citizenship and materialize data through do-it-yourself sensing devices. The research is funded by a European Research Council grant for a project called "Citizen Sensing and Environmental Practice".