Buried in this post on O'Reilly Radar is the idea of doing large-scale, distributed scientific studies using consumers' hand-held devices. I can imagine health and human services releasing a mobile phone app that lets you measure, for instance, radon gas levels ... and then all the individual data sets getting uploaded to a central server that can look for larger trends.
Printable electronics are getting so easy ... they could print the sensor on postcards that you cut-out and wedge in your phone's USB port. How about a lead sensor on a postcard? How about water quality? Grassroots campaigns could print sensors and hand them out in neighborhoods they want to mobilize.