(By Nina Adam and William Wilkes) Patrick Paumen doesn’t have to worry about forgetting his keys and being locked out of his apartment. That is because he doesn’t need a key anymore—he simply unlocks the door with a wave of his hand. The 32-year-old IT expert from the Dutch city of Heerlen is one of a growing number of people with electronic implants under their skin, mostly to use as keys or for identification.

Mr. Paumen has several such implants, or tags, embedded in the fatty tissue of his hands and his lower arm. He uses separate tags to unlock not only his apartment door, but also his office and the gate to a secure parking lot at work. Another stores information he would otherwise put on a business card—name and contact details—and yet another holds similar information for nonbusiness encounters. READ MORE