It's a parent's worst nightmare. Their child doesn't come home one evening and is missing for several days.

When a 14-year-old boy from Atlanta, Georgia disappeared earlier this year, his mother turned to her smartphone for clues using an app called Family Tracker that helped track his location.

It is one of several apps that allow parents to track the whereabouts of their children.

"You can see where your loved ones are without having to call or bother them," said Roberto Franceschetti of LogSat, the creators of the Family Tracker, which has more than 100,000 users and is available worldwide.

Parents can track the location of their child on a map, send messages, and even activate an alarm on the phone remotely.

"We have an option for the sender to make a very nasty, noisy sound. It's a loud siren and we repeat that sound every two minutes until the person picks up," he said.

Parents don't need to own a smartphone to track their children. The service is also accessible via the web, as long as the phone that is being tracked is running the app, which runs on an iPhone or Android devices.

Family Tracker has an additional service that keeps a log of all data generated by the app for a two-week period, which the company calls GPS breadcrumbs.

The service was used to find the missing boy in Atlanta.

"With a subscription, we keep all the locations where people have been on our servers. You can see where your kid has been for the past two weeks. You can find out where someone was at a certain time, or when that person was at a specific place," Franceschetti explained.

"When somebody gets abducted, usually whoever does this throws the phone away or takes the battery out. We were hoping that our app would at least provide information on where the person was abducted or where they had been in the past, that way the police would have a history or some clues as to who they may have been seeing."

But are these types of apps an invasion of privacy?

"The advantages are huge compared to the disadvantages. Let's not forget that the person always has to give initial permission -- no one can be tracked unless they allow someone to do it," said Franceschetti.

(Read by Emily Cheng. Emily Cheng is a journalist at the China Daily Website.)

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(Agencies)