In 1999, a team of researchers at Accenture described what you now know as a barcode-scanning app on your phone; they called it Pocket Bargain Finder. Pocket Bargain Finder "combines the global scope of Internet shopping agents, the ease-of-input of a barcode scanner, and the portability of a PDA. The result is a convergence of electronic and physical commerce that we call augmented commerce." In their research paper (pdf), the authors have described the potentially disruptive effects such technology would have on traditional retailers: "With consumers able to find the best price regardless of where they shop, the physical retailer is left at a distinct disadvantage." (Related from AdLab a few years ago: The Future of Retail: Instant Price Check.)
This is apropos of the Price Check for iPhone, a new app that Amazon launched today that lets you scan barcodes, snap pictures or say the product name into it and it will show you product prices, reviews and ratings along with a big Buy On Amazon button.