Windows Phone has built-in QR scanning capability. It was integrated into the OS as part of the last major update (7.5/Mango). It's a feature of 'Bing Vision'

Windows Phone has built-in QR scanning capability. It was integrated into the OS as part of the last major update (7.5/Mango). It's a feature of 'Bing Vision' which allows scanning of QR Codes, Microsoft Tags, Standard Barcodes, and Text. This is built-in to the general Bing (Search) feature of the OS and is avaliable on all Windows Phone devices.