Big cities use sensors in strategic spots to monitor environmental conditions, but they're not much help when there's a localized problem far from the nearest monitoring station. La Montre Verte (The Green Watch) from a French group called Fing, turns regular citizens into walking sensors, by sending data by cellphone about noise and ozone levels, which can then be compiled and mapped to show trouble spots. A pilot program was completed in Paris earlier this year, followed up by a much larger test last week at the Picnic '09 conference in Amsterdam. And yes, it even tells the time.
My only question is what happens to the noise sensor if you go out clubbing? Not to mention how the ozone readings looked around some of Amsterdam's famous "coffee shops".