The use of microchips to track people (such as those embedded in hospital wristbands) and products (those uncomfortable tags on clothing that have to be cut off prior to wearing) has come under fire from civil rights groups who claim that big corporations are using this technology as a tool for spying. But what about when these tags are embedded in people themselves, rather than the things they wear?

That's what Mexican security firm Xega SA, which sells technology for tracking people, wants to do, particularly in cases when people are held for ransom. For about $3,700, the company will implant a chip the size of a grain of rice (it costs another $1,800 per year for monitoring), reports the Telegraph. Although it is unclear where the chip is likely to be implanted in a person's body its customers carry with them a panic button that can be pressed if a person feels he or she is in danger. A transmitter then sends signals via satellite to pinpoint the location of the person in distress, reports Reuters. (Xega did not respond to requests from for an interview).

It's perhaps the next obvious step in radio-frequency identification (RFID) technology, which companies already use to gather information about consumer behavior that can be used as a marketing tool, to track merchandise in order to protect themselves from shoplifting, and to locate patients who've wandered away from hospital beds. Xega's technology is troubling in a number of ways, in particular that there's a market for it in countries including Brazil, Colombia, Mexico and Venezuela.

But there are also several questions about whether the technology will actually work in an emergency. Implanted chips have been used in self-experimentation (such as England's self-styled cyborg Kevin Warwick) and by security contractors to automatically communicate their security credentials over short distances to gain access to a secure facility . While Warwick was actually plugged into a computer, the alternative has been to send and receive information via RFID, even though this technology has a limited range (in most cases about 25 feet) and the signal can be weakened by any metal that comes between the RFID reader and the tag, says Roy Want, a principal engineer at Intel Research/CTG in Santa Clara, Calif.

A chip that relies on GPS poses a whole new set of challenges. For one, the chip would need an antenna and radio as well as a battery powerful enough for its signal to reach a satellite network. "I'm skeptical," Want says, "that you could build something that could reach a satellite and yet be small enough to put under your skin."

Other problems are more logistical than technical. When the person's captor finds out about the embedded GPS beacon, it would likely be removed in a very painful way and be rendered useless if the captive is moved to a new location. Additionally, sometimes knowing where a captive is being held is only part of the problem, particularly if the captive is being held by guerilla forces situated deep in the Amazon, which is the case in several South American countries (the rescue of Colombia's Ingrid Betancourt and three American security contractors provided some insight into the plight of these captives).

Still, with kidnapping becoming a lucrative industry in several countries (often as a means of funding anti-government rebels), technology such as what Xega is proposing would be welcome as another tool for law enforcement to work with.

(Image courtesy of iStockphoto; Copyright: Dave Pilibosian)