Microsoft Tag connects almost anything in the real world to information, entertainment, and interactive experiences on your mobile phone. Tags are a new kind of bar code that can be displayed anywhere. You can add a Tag to your ads, posters, product packages, flyers, display it on your website, billboards, clothing…the list is endless. When you scan a Tag by using the free Tag Reader application on your mobile phone, it will automatically open a webpage, display a message, or dial a number – there are no long URLs to type or SMS messages to send.

http://tag.microsoft.com/overview.aspx