A method of maintaining a status of a product item is provided. The product item includes an associated interface surface which has coded data including a plurality of coded data portions indicative of the product item's identity. The method includes, in a sensing device, sensing at least one coded data...http://www.google.com.au/patents/US7946485?utm_source=gb-gplus-sharePatent US7946485 - Method of maintaining product status with invisibly coded interface
