The Air Quality Egg is a sensor system designed to allow anyone to collect very high resolution readings of NO2 and CO concentrations outside of their home. These two gases are the most indicative elements related to urban air pollution that are sense-able by inexpensive, DIY sensors.
The Air Quality Egg is developed by a community effort, born out of groups from the Internet of Things Meetups in NYC and Amsterdam. The groups consist of designers, technologists, developers, architects, students, and artists.
For more see: http://airqualityegg.com/
Photo source: http://airqualityegg.net/author/daniel/