Clean Space Tag

This looks really interesting, but a little expensive perhaps for geography departments who will not necessarily use it

At the moment Clean Space offer air quality mapping of London in particular.

There are various iPhone and Android apps.

The sensor measures air quality

Last year, I was involved in the DISTANCE project with INTEL and Sciencescope and other partners, including Explorer HQ of course.
You can search the blog to find relevant posts. Happy to trial this new entrant into the field of air quality monitoring...