[Todd Russell]

Are you talking about QR Codes by chance? A lot of libraries and others are using them to include additional information for those with QR Code readers (free or pay apps that use the camera on a phone to analyze the code and share the meaning). Here's an example of the brochure from our local library showing where they used a QR Code:

QR Codes:

Although initially used for tracking parts in vehicle manufacturing, QR codes now are used in a much broader context, including both commercial tracking applications and convenience-oriented applications aimed at mobile phone users (termed mobile tagging). QR codes may be used to display text to the user, to add a vCard contact to the user's device, to open a Uniform Resource Identifier (URI), or to compose an e-mail or text message. Users can generate and print their own QR codes for others to scan and use by visiting one of several paid and free QR code generating sites or apps.

I used a QR Code on the back of my paperback near the serial code to embed a special URL. Most phones have apps with free QR Code readers. They are kind of fun because they will take you to places on the web to learn more or show a short text message.

 

[Todd Russell]

Looks like while I was working up my post others answered before me

I think you're talking about QR codes. They can be scanned with smart phones and take the user directly to a website or app. In the bookstore I'm an owner of, we put them on the shelves of books that are available in Google e-books editions, so if a customer would rather have an e-book than a printed one, he or she can scan the QR code and buy the e-book on the spot.

This is a good idea, especially if these are affiliate URLs so your bookstore gets a spiff in the process