Wikipedia describes QR tagging thus...

Although initially used for tracking parts in vehicle manufacturing, QR Codes are now used in a much broader context, including both commercial tracking applications and convenience-oriented applications aimed at mobile phone users (known as mobile tagging). QR Codes storing addresses and URLs may appear in magazines, on signs, buses, business cards or just about any object that users might need information about. Users with a camera phone equipped with the correct reader software can scan the image of the QR Code causing the phone's browser to launch and redirect to the programmed URL. This act of linking from physical world objects is known as a hardlink or physical world hyperlinks. Users can also generate and print their own QR Code for others to scan and use by visiting one of several free QR Code generating sites.

MY COMMENTS

Creative use of these tags in poster campaigns and other outdoor media can help drive immediate traffic to particular websites by those mobile phone users equipped with tag readers - available free for most phones!

Try it yourself. You can find a load of readersfrom the list below...

Beetag - These guys provide a reader that reads beetags, qr codes and datamatrix codes, or so they say. Yet to be tested. The list of supported handsets is impressive.

Glass - A reader devised by the active print project created by HP Labs in Bristol. They look promising in their proposal of a mobile codes consortium, but considering their latest news is dated January 2007 I am not entirely convinced they deliver what they say they will. The glass reader is also a .SIS file which doesn’t work on my Nokia N70’s.

I-nigma - One of the easiest to use, but they don’t update their website with new handsets and ignore emails for support.

Kaywa - Thse guys get a lot of good reviews, but I haven’t been able to overcome the .SIS download prob with my Nokia N70’s

Neoreader - Good reviews, but quite a limited number of handsets that they will work on, Brands they support are: Apple, Blackberry (but only a few), Nokia, Motorola (very limited range), Siemens, Samsung and Sony-Ericsson.

Nokia – Readers are loaded onto newer handsets. Not very backwards compatible, even with symbian phones. They do have good support in their Nokia beta-labs though which a rich community of enthusiasts and developers.

Quickmark - Supports a range of codes: quickmark, qr codes and datamatrix codes. Quickmakr is Taiwan based and provides good support and a range of code options.

Scanlife - US based company which supports by operating system, rather than handset: Android , Blackberry, Palm OS, Windows Mobile, Symbian and iphone. They have accounts so you can manage tags online as well.

Shotcode - Supports only Shotcodes. These are propriety codes aimed at advertising, so not that popular with end users. Devised by High Energy Magic, a spin out company from sources of Cambridge University in the UK. Mostly linked in with advertising for companies such as Coca Cola, Heineken, Xbox, Nike, Volkswagen, Monsterboard, Jameson Whiskey

Trillcode - Only reads trillcodes, and from the website difficult to work out which handsets are supported. Trillcodes do allow for branding or images to be embedded in the codes. They were evised by Lark Computers in Romania, but since they are propriety software, with little publicity in Western Europe they do not really have that much of the market.

Upcode - Can read datamatrix, qr-code and upcodes, which are propriety so limited in their use and really used by wide market share.

2D Sense - iPhone app which reads a wide variety of codes: Aztec, QR, Blot code, Datamatric, and Shotcode. It gets pretty bad reviews on a lot of sites though, so I think only the lucky ones can get it working.