After years of helping to locate stolen automobiles, global positioning satellite (GPS) technology may be about to graduate to a new class of personal security devices that could track everything from missing children to lost mountain bikes to Alzheimer's disease patients.

Using postage-stamp-sized GPS boards, makers of security hardware will begin in September to roll out wristwatches and pager-sized units that can be used to track lost individuals to within a few feet. And one company even plans to unveil a working prototype of an encapsulated GPS device that could be surgically implanted inside a person's arm.

The move toward such personal security items represents another potential market for GPS, which has yet to fulfill predictions that it is the next big thing in cell phones and automobiles. Experts foresee the miniaturized technology being employed on motorcycles, high-end bicycles, appliances and containers of all sorts, in addition to wristwatches and wearable personal security devices for people.

"By 2006, we expect this to be a $20 billion industry," said Timothy Neher, founder, president and chief executive officer of Wherify Wireless Inc., which will roll out the world's first GPS tracker for children in September.

Wherify's GPS Locator for Children, which is expected to touch a nerve with parents concerned over the recent wave of child abductions, is the first in a series of products from the company aimed at locating individuals. The wristwatch reportedly discourages wrongdoers because it is made from a cut-resistant material and can be locked on a child's wrist using a tiny onboard motor and tamper-resistant sensors. The unit, priced at $400, incorporates a GPS transmitter and receiver, a 1,900-MHz full-functioning cell phone, a lithium ion battery and two antennas.

Experts foresee a strong demand for the technology, despite the fact that the risk of child abduction is minuscule. "Statistically, kidnappings are about as likely as being struck by lightning," said Paul Saffo, a director of The Institute for the Future (Menlo Park, Calif.). "But just because it's unlikely doesn't mean that a lot of parents won't want to put GPS units on their kids."

Saffo believes that the use of GPS technology in wristwatches may only be the tip of the personal security iceberg. "GPS has already proven itself in military applications," he said. "Now it's going to be popping up everywhere. It's clearly a consumer phenomenon."

Miniaturization effort

The key to the sudden emergence of GPS in personal security devices is the rapid downsizing of GPS chip sets and supporting circuitry. Such applications would have been impossible five or six years ago, when automakers were proudly touting tape-deck-sized GPS units in the trunks of Cadillacs, Lincolns and other high-end vehicles.

But product manufacturers have changed that scenario by working closely with chip makers. For example, Wherify spent the past three-and-a-half years partnering with Sirf Technology Inc. (San Jose, Calif.), a maker of GPS chip sets. Sirf, whose chip sets can make GPS signal-acquisition technology available as a block to a host processor, helped Wherify engineers to reduce their GPS boards to about the size of a postage stamp.

The company also reduced the physical size of the unit by employing a scheme in which the GPS device does not need line-of-sight clearance to the satellite, but uses a triangulation technique that involves catching reflected signals. That required the company to develop its own custom software. "It's a little trickier putting everything together when you're trying to triangulate a bouncing signal," said Neher of Wherify. "But that's the key to making it smaller and making it work inside of concrete buildings."

Neher demonstrated the technology for EE Times while sitting in a concrete building that has titanium-shielded windows. His location, which was established by the Global Positioning Satellite, was relayed via onboard cell phone technology to a data center, then was displayed on the Internet within seconds.

Similarly, Applied Digital Solutions (Palm Beach, Fla.) has said that it ultimately plans to put its GPS circuitry on a board smaller than the diameter of a quarter and then create a "subdermal" personal location device that could be planted in a fleshy area of the body, such as the upper arm. The device, which would then report a person's whereabouts via cell phone technology, builds on the company's earlier technologies, which involved using implantable chips to identify individuals to a nearby scanner.

Applied Digital engineers say that the key to their miniaturization effort is that their GPS unit receives but does not transmit data. Instead, it passes longitude and latitude information over to a wireless cellular network that coordinates the data to a mapping engine.

"We depend on the cellular network to avoid the power consumption and size issues of a traditional GPS receiver," said Keith Bolton, chief technology officer. "It's a lot like the Internet, where a router does a lot of the thinking instead of letting a modem or a desktop device do it. We depend on the network not only to shrink the size of the GPS unit, but to drive the price down."

Applied Digital said that the personal locator might use a hardware scheme in which supporting GPS circuitry wraps around a pill-shaped antenna, like a bun around a hot dog. Power could be delivered to the device through remote charging devices, like those used in some pacemakers, which charge through the skin. Working prototypes of the device are expected by December of this year.

Makers of GPS-based personal security technology believe the demand for their devices will grow rapidly. Wherify expects to sell approximately 200,000 of the GPS-based wristwatches during the coming year and then plans to sell millions of a follow-on GPS wristwatch that will be about half the size of the current model.

Although doubters have been quick to point out that such wristwatches could be disposed of by potential kidnappers, Wherify executives say that several built-in features prevent that from happening in most situations. "If a seven-year-old is walking to school and feels endangered, he or she could push a button on the watch and lock it in place," Neher said. "If the situation escalates, the child could push two more buttons and the system would automatically call 911."

"Ultimately, we hope the technology will be a deterrent," Neher added. "If predators see this, we hope they will go right past the child."

Wherify said it soon plans to release a similar product for Alzheimer's patients, who tend to wander away. The company is also working with OEMs in vehicles and on high-end bicycles, Neher said.

Other companies are following suit. Digital Angel, a sister company of Applied Digital Solutions, now offers a GPS unit that can be clipped on a belt. GPSTracks (Dallas) is also developing a product to be clipped on clothing.

Most of the new breed of security device manufacturers say they are not worried about privacy concerns because the technology is optional. Some South American officials have expressed interest in such systems because kidnappings have reached epidemic proportions in countries such as Brazil, where kidnappers are now said to be targeting government officials as well as children under 10.

Ultimately, however, experts foresee consumers boosting the technology's popularity by finding unadvertised uses for it. "Forget getting police access to location when someone calls 911," said Saffo of The Institute for the Future. "Every parent's dream is to have the phone tell them where their kid is when he calls home late at night."