There is no more hassling with house keys for Amal Graafstra because the key to opening his door is always at his fingertips, literally.

Graafstra has radio frequency identification microchips implanted in his hands. When used with RFID readers, they allow him to control devices around his house.

"There's a small 3-millimeter-by-13-millimeter glass RFID tag in both the right and left hands. I can get in my front door, in my car door, and log into my computer," Graafstra said.

Mikey Sklar is also chipped and now gets bombarded with questions from the curious on his Web site.

"I usually get questions about why I did this implant and where they can find out some more information," Sklar said.

Alex Pang with the Institute for the Future said techy-types are taking RFID to the next step.

"They want to experiment with it and sometimes use themselves as the experimental subjects," Pang said.

But are these experiments safe? Graafstra and Sklar's chips are not approved by the Food and Drug Admistration. In fact, there is only one device approved for human implantation and it's for medical purposes.

Both got their tags from a tech Web site and persuaded surgeon friends to do the implants.

"I'm not worried about any kind of ill effects," Sklar said.

But the FDA warns of risks like rejection or infection with any RFID implants. And when it comes to the unapproved chips, the agency hopes "the physicians performing these procedures are doing so under proper clinical circumstances" and wants to make sure patients are told of the risks.

But health risks aren't the only concern.

"There is a potential for a security problem," privacy expert Liz McIntyre said.

McIntyre said there is proof hackers can clone RFID chips. And if people program tags with credit card, bank account or medical information, the risk of identity theft goes up.

And if you think replacing a credit card is a hassle -- "You can imagine if you have a tag in your body, getting that changed is a surgical procedure rather than a number of phone calls," Pang said.

Graafstra and Sklar said they don't feel at risk and love what's slipped under their skin.

"I don't see how people are going to take advantage of me. If someone really wants to get into my particular house, there's a lot easier ways to do it," Graafstra said.

The FDA said health concerns are not just about infection or rejection.

They said the tags could potentially migrate, travel in the body or even cause MRI incompatibility and electromagnetic interference.

The company selling Graafstra and Sklar's chips has a large disclaimer on its Web site stating the chips are not intended for human implantation or medical use.