Late last year, Google announced that it was sending traditional brick and mortar businesses bar code decals to put on their windows, with these QR barcodes (a two-dimensional barcode that represents the URL of the company’s local listing) people can scan them outside with their phones and bring up business listings with all kinds of information like, reviews, menus, contact info, etc...
These codes have been made available to the businesses Google deemed "favorite places". It began with over 10,000 businesses in the US that received them right off the bat, and Google will eventually expand that number in the future.
While the intent is to place these decals outside of your physical business the real implications could be used on advertising in all media. Since the barcode can be scanned from just about any type of media including billboards, business cards, computer monitors (try the example above), TVs, and possibly even movie theater screens as well the opportunities for advertisers to use these codes is endless.