Implanted ID chips are used by some farmers to keep tabs on their livestock. Now a company that manufactures them, Applied Digital Solutions, is trying to get people used to the idea of implanted chips in humans.

These chips can hold a few sentences of information and show great potential for being teamed up with a National ID card system.

See the articles:
A Chip ID That's Only Skin-Deep, by David Streitfeld for the LA Times.

and

Next: An ID Chip Planted in Your Body? , by Robert O'Harrow Jr for the Washington Post.