SCVNGR is a platform for quickly and easily building location-based mobile games. Each game is all about doing challenges at places. Go here and take a photo, go there and solve this riddle. You happen to be at this coffee shop? Awesome! Try this challenge and earn a couple points! SCVNGR powers games for all sorts of institutions ranging from Princeton to Harvard to the Smithsonian Institutes to SIGGRAPH and even the U.S Navy. “A new option, that we're launching, uses QR codes planted at locations within the game-board. Players must scan these QR codes to verify that they've made it to the right spot. We're using the Google Charts API as an easy way to programmatically generate QR codes. Of course, generating and planting the QR codes is only half of the equation. You've also got to be able to decode them from the phones during the game. We experimented with a couple of options as to how to best achieve this. So we turned to the ZXing project (pronounced Zebra Crossing) which is an open source barcode processing library written in Java and highly suited to the Android environment,” revealed.
More info: SCVNGR