AP report indicates that several studies have shown implanted chips can cause cancer in mice. Now that's a long way from non-implanted chips in humans. But it makes you wonder about a bunch of radio transmitters in your pocket a few inches from sensitive spots.

Interesting tidbit; implantation of the chips was approved by the Department of Health and Human Services, which, at the time of VeriChip's approval, was headed by Tommy Thompson. Two weeks after the device's approval took effect on Jan. 10, 2005, Thompson left his Cabinet post, and within five months was a board member of VeriChip Corp.