The Register - High-tech tattoo more than a pretty picture
Here is a news report on a new approach to identification verification that combines the simplicity of a tattoo with the technology of radio frequency tagging:

Somark Innovations, a small company working out of Saint Louis, has successfully tested an RFID tattoo, on cows, mice and rats: enabling an identifying number embedded under the skin to be read from over a meter away. [...] Somark are in the process of raising money to exploit the technology, and point out that what works for animals can, of course, also work for people; identifying Military Personnel as one of their secondary markets, after cattle and other livestock.

We had many debates about the Mark of the Beast (Rev 13:16-18) on the Bible Prophecy-L discussion group and there were always many people who rejected the notion that the mark would be technological, insisting that it could be something as simple as a tattoo. Perhaps it will be both?