The first step is to plunk down a couple hundred dollars for a web-browsing smartphone, which the New York Times contends will end up saving users money by helping shoppers make smart decisions. (Be sure to offset the coltan-mining you are financing by your purchase with a donation to the late Dian Fossey's Gorilla Fund, and resolve not to buy a new phone for at least three years.) Having done that, it’s time to load up on specialized applications. The cleanest and greenest of the mobile bunch is GoodGuide, a database that ranks products by their environmental merits—or, more likely, their inadequacies. It just became available as an iPhone application through Apple’s App Store, which is likely to increase its reach and user base quite dramatically. (Previously GoodGuide had been sequestered to the generally home-based world of internet shopping.) Now shoppers staring at actual items in actual stores can enter a product’s name or UPC code and look up, for example, the toxicity of its ingredients compared with its competitors. (A version of the program for Android, the smart phone software from Google, is expected to be released in a few months.)

To compile the social-environmental profiles for its product database, GoodGuide pulled together a team of scientists and tech gurus to unearth information on the environmental, social, and health affects of about 60,000 products. At least for now, the database seems to be somewhat focused on personal care products, such as sunscreens and household cleaners. In September, GoodGuide got very positive reviews from the crowd at TechCrunch50, the technology blog’s conference for start-ups.

There are other options and ways to smarten up your shopping experience, of course. If you have Android, get familiar with your barcode scanning options. Several apps allow users to comparison-shop, read reviews, and even calculate how much a shopper is likely to spend on gasoline in the process. Because at the end of the day, a phone is only as smart as its owner. And when it comes to buying things, being smart means being sustainable.