ack154 writes "The Register reports that a St Louis based company, Somark Innovations, has successfully tested RFID tattoos to be used for tracking cattle and other animals. Details are limited for the actual tattoo, but it's said to contain no metals and can be read up to about four feet away. Engadget has some more details on the matter. And yes, the article does mention RFID tattoos are possible for people, specifically the military. From the article: 'The system developed by Somark uses an array of needles to quickly inject a pattern of dots into each animal, with the pattern changing for each injection. This pattern can then be read from over a meter away using a proprietary reader operating at high frequency.'"