Updated

From little ones prone to running off in crowds to big kids hitting the road for the first time, a bunch of new devices claim to help parents keep an "eye" on their children — even when they're not around.

The most controversial of these gadgets is an under-the-skin personal location device from Applied Digital Solutions. Using Global Positioning Satellite technology, a microchip surgically implanted in the body finds children and notifies parents of their whereabouts.

ADS says the device, which is the size of a wristwatch-face and may become even smaller, could be used to find kidnapped children, locate young kids who wander away from parents and track teens who participate in at-risk behavior.

"With an implanted device, the child doesn't have to remember to wear it. It can't be lost or stolen or stripped away. And it's totally concealed," company spokesman Matthew Cossolotto said.

A prototype will be available later this year. In the meantime, ADS already manufactures two similar products: VeriChip and Digital Angel.

Cossolotto says VeriChip ($200 plus $9.95 a month), an under-the-skin, tamper-proof method of identifying one person against another, could help prevent kidnappings like the one of Utah teen Elizabeth Smart.

"The chip would have realized that the intruder did not have permission take the girl from her home," Cossolotto said.

Digital Angel ($399 plus $29.95 a month) is a wearable GPS device that indicates when a person has moved beyond certain preset boundaries. The alerts may be sent to cell phones, computers or pagers.

"The chip has an alarm button and is hidden from any perpetrators," Cossolotto said.

Another up-and-coming product is Safe Force ($280), a "black box" for cars similar to the flight data recorder used on planes that monitors drivers' performance.

Safe Force, made by Calif.-based Road Safety, operates through a series of audio warnings that sound when a driver speeds, starts hard, breaks hard, or generally drives aggressively — and don't go away until the driver changes his behavior.

"It's like being able to sit next to your teenager every time they drive," Road Safety CEO Larry Selditz said.

Safe Force will be available in November; a GPS add-on is in development.

GPS, however, has its limitations. Buildings can impede signals and the technology is subject to the problems of cell phones and computers.

Nevertheless, many feel these devices are nothing short of miraculous.

"I've gotten over a thousand enthusiastic e-mails about Safe Force; only two complained about Big Brother invasions of privacy," Selditz said.

One famous parent, America's Most Wanted host John Walsh, whose 6-year-old son was kidnapped and killed in 1981, said GPS could be "lifesaving" on a recent episode of Larry King Live.

"It's a brilliant idea. I wish someone would develop it because, number one, time is crucial when a child is missing and you could locate them by the chip," he said. "And even if you weren't lucky enough to locate them, finding the body is crucial for two things: the ending of the search of the parents and helping with the prosecution of the case."

Other parents were more skeptical.

California resident Gina Brodt said she'd never put anything under her child's skin, but she might have considered using Digital Angel when her daughter was younger.

"I had a little one who liked to run off in the mall," she said. "I might have bought it for her."

Family Circle contributor Annie Pleshette Murphy said teaching kids to police their own behavior is the key to keeping them safe.

"So many of these devices prey on a parent's wish to protect their child 100 percent of the time," she said. "One of the hardest things about being a parent is accepting that you can't do this."