Backed by Hewlett Packard, Mobile Bristol is another player in the physical world connection space.
From PicturePhoning.com ,
Active Posters are standard printed advertising posters that would be found on hoardings, at bus stops, outside cinemas or the Underground. Unlike standard posters, they have special "barcodes" printed on them.
These are read using standard camera phones and link the poster to online content, applications and services. For example, one could "click" on a poster to download music, buy tickets to a show, order a taxi or answer quiz questions. Each active poster can have its own unique barcode, so the service offered can be specific to a particular location.
For example, a shop near to a particular bus stop could offer a special discount on an advertised product. The special barcodes can link any printable surfaces such as books, magazines, leaflets and stickers in addition to certain types of digital display screens to on-line content in all kinds of urban/suburban/rural situations."