Cardstar's iPhone app was one of Best App Site's 10 Best iPhone Apps for 2009. Cardstar allows users to stop carrying around customer loyalty cards, frequent flyer cards and any other card that renders a machine readable bar code as an identifier. Cardstar's proprietary technology allows for a bar code to be rendered on a smart phone (such as an iPhone), which is scanned at the point of sale in lieu of a physical card. Merchants where Cardstar is currently being used include Best Buy, CVS, Giant, Costco and many others. If you have an iPhone and don't use Cardstar, you should.