According to the FBI's National Crime Information Center, 836,131 persons were reported missing in 2006. About 80% of those were juveniles (persons under 18 years of age), the overwhelming majority of which were girls. While most missing persons return home safely, that statistic shows that 2,290 times per day, parents or primary care givers felt the disappearance was serious enough to warrant calling law enforcement. Even more troubling, the number of missing persons reported to law enforcement has increased almost 500% in the past 20 years.

What if, instead of sitting at home in a terrified panic that harm has come to your child, you could instantly locate him or her on a map, pinpointing their exact whereabouts? That's the promise behind a new wave of GPS and RF (Radio Frequency) tracking devices aimed at helping parents keep electronic tabs on their children. I've spent the last few months testing a number of these products at length, sorting out the good from the bad.

The bottom line? Hollywood-style GPS tracking still eludes us, but there are some good products available that will indeed help parents keep track of AWOL kids. There's also some duds out there that either underperformed or simply don't work at all. Read on for the full review, including which products I recommend, and which ones you should avoid.

First, a quick primer on the different technologies involved: A-GPS, or Assisted GPS leverages both cellular and GPS technology. A-GPS devices determine their position using traditional GPS technology, but upload this information back to you via cellular technology. A-GPS devices are essentially GPS-enabled cellular devices, and therefore require a monthly service charge for the data. Monthly service fees range from around $20 - $50 per month, depending on the usage plan you choose.

RF tracking devices don't use GPS at all, and instead rely on Radio Frequencies to determine positioning information. RF devices are well suited to indoor tracking and are aimed at helping parents keep track of kids at the mall, playground, supermarket, or any other short distance.