Eric Paulos of Intel Research has launched an SMS system for mobile phone users in the US to learn about the quality of the air around them. Called Ergo, the system uses data from the US Environmental Protection Agency's airnow.gov site and Weatherbug.com. The number to text is 415.624.6678 and here's a a summary of the commands:

If you text...

* a 5 digit zip code = you receive the most recent air quality reports for that area (ex. 94704)
* the word worst = you receive the worst three locations in the US as currently reported (ex. worst)
* daily zip time = you receive a report every day at the specified time for the given zip code.