Technophoria: They Loved Your G.P.A. Then They Saw Your Tweets.

Perhaps she hadn’t realized that colleges keep track of their social media mentions.

“It was incredibly unusual and foolish of her to do that,” Scott A. Meiklejohn, Bowdoin’s dean of admissions and financial aid, told me last week. The college ultimately denied the student admission, he said, because her academic record wasn’t competitive. But had her credentials been better, those indiscreet posts could have scuttled her chances.

“We would have wondered about the judgment of someone who spends their time on their mobile phone and makes such awful remarks,” Mr. Meiklejohn said.

As certain high school seniors work meticulously this month to finish their early applications to colleges, some may not realize that comments they casually make online could negatively affect their prospects. In fact, new research from Kaplan Test Prep, the service owned by the Washington Post Company, suggests that online scrutiny of college hopefuls is growing.

Of 381 college admissions officers who answered a Kaplan telephone questionnaire this year, 31 percent said they had visited an applicant’s Facebook or other personal social media page to learn more about them — a five-percentage-point increase from last year. More crucially for those trying to get into college, 30 percent of the admissions officers said they had discovered information online that had negatively affected an applicant’s prospects.

“Students’ social media and digital footprint can sometimes play a role in the admissions process,” says Christine Brown, the executive director of K-12 and college prep programs at Kaplan Test Prep. “It’s something that is becoming more ubiquitous and less looked down upon.”

In the business realm, employers now vet the online reputations of job candidates as a matter of course. Given the impulsiveness of typical teenagers, however — not to mention the already fraught nature of college acceptances and rejections — the idea that admissions officers would covertly nose around the social media posts of prospective students seems more chilling.

There is some reason for concern. Ms. Brown says that most colleges don’t have formal policies about admissions officers supplementing students’ files with their own online research. If colleges find seemingly troubling material online, they may not necessarily notify the applicants involved.

“To me, it’s a huge problem,” said Bradley S. Shear, a lawyer specializing in social media law. For one thing, Mr. Shear told me, colleges might erroneously identify the account of a person with the same name as a prospective student — or even mistake an impostor’s account — as belonging to the applicant, potentially leading to unfair treatment. “Often,” he added, “false and misleading content online is taken as fact.”

These kinds of concerns prompted me last week to email 20 colleges and universities — small and large, private and public, East Coast and West Coast — to ask about their practices. Then I called admissions officials at 10 schools who agreed to interviews.

Each official told me that it was not routine practice at his or her institution for admissions officers to use Google searches on applicants or to peruse their social media posts. Most said their school received so many applications to review — with essays, recommendations and, often, supplemental portfolios — that staff members wouldn’t be able to do extra research online. A few also felt that online investigations might lead to unfair or inconsistent treatment.

“As students’ use of social media is growing, there’s a whole variety of ways that college admissions officers can use it,” Beth A. Wiser, the director of admissions at the University of Vermont, told me. “We have chosen to not use it as part of the process in making admissions decisions.”

Other admissions officials said they did not formally prohibit the practice. In fact, they said, admissions officers did look at online material about applicants on an ad hoc basis. Sometimes prospective students themselves ask an admissions office to look at blogs or videos they have posted; on other occasions, an admissions official might look up an obscure award or event mentioned by an applicant, for purposes of elucidation.

“Last year, we watched some animation videos and we followed media stories about an applicant who was involved in a political cause,” says Will Hummel, an admissions officer at Pomona College in Claremont, Calif. But those were rare instances, he says, and the supplemental material didn’t significantly affect the students’ admissions prospects.

Gadgetwise Blog: Tracking Loved Ones on the Grid

So the other day, I slipped a GPS tracking device into my wife’s car before she headed off to work. I put another tracker in my 2-year-old’s diaper bag and sent him off to the nanny for the day. I still had a few trackers left, and my parents were in town, so I also threw one into their vehicle while they took my son out to the park.

Of course, I had never suspected any wrongdoing and, later on, when I reviewed the trails left by these GPS devices, they turned up nothing untoward. My spying was meant only as an experiment, but I still felt like a heel.

As well I should have. It’s precisely because of mischief like mine that tracking devices get a bad rap. These small gadgets work by connecting to GPS satellites and cellular networks to follow subjects and report back their locations to their masters. Once I sent them out into the world, I could look up the trackers online, either on the Web or through a smartphone app. They could also be configured to send me alerts based on various criteria. If my wife’s car left her office parking lot during the day or my parents’ vehicle broke the speed limit, I might get a text alert. If your mind reels at the universe of Maury Povichian possibilities contained within these gadgets, you’re not alone.

Yet after chatting with representatives at several GPS tracking companies and trying out their products, I learned that there are many less icky, entirely defensible uses for such devices. For example, some parents use trackers to make sure their children get to school and back safely each day. Others build them into their teenage drivers’ cars so they can be alerted if the kids drive recklessly. There’s also the elder-care market — GPS trackers embedded into medical-alert devices can help locate and provide emergency help for parents with Alzheimer’s.

And don’t forget the dog: a tracker attached to its collar can let you know if it wanders out of your yard, and help you find it if it doesn’t come back. The more I heard about these devices’ applications, the less unseemly they began to feel; indeed, for many people, GPS tracking could soon become a regular part of life.

Among the companies pushing for this future is Amber Alert GPS, a Utah-based firm that was founded in 2007 after Russell Thornton, a businessman, lost his 3-year-old son at an amusement park. After a frantic 45-minute search, Mr. Thornton found the boy hiding in a play structure, but he was traumatized by the incident, and it spurred him to build a device that would help other parents avoid that fate.

Amber Alert’s tracker is about the size of a child’s palm, and it looks a bit like an old-school pager. It can be slipped into a pocket or backpack, or placed in a carrying case attached to a child’s belt loop. According to Carol Colombo, the chief executive of Amber Alert GPS, most customers buy the device for children between the ages of 2 and 10 — children old enough to be mobile, but too young to carry a cellphone. Still, the Amber Alert can act as a quasi-phone; with a press of a button on the device, your children can send a text or initiate a voice call with you, and you can also dial in to the tracker and listen to their surroundings.

I found the Amber Alert extremely simple to set up and use. The company’s Web site, which allows you to configure and monitor the tracker, is well designed and intuitive, and its iPhone and Android apps also work quite well. Amber Alert offers more customizable alert settings than any other child-tracking system I tested: among them, there’s an option to receive an alert each time your child comes within 500 feet of an address listed on a sex-offender database.

The only downside to the Amber Alert is its price. The device sells for $200, and it requires a service plan, which goes for $14.99 a month for basic tracking features, and $24.99 a month if you would like extras, including voice-calling and sex-offender alerts.

Another child-tracking device I tested, the Securus eZoom, is slightly larger than the Amber Alert and doesn’t have some of that device’s advanced features (like voice calling), but it is also significantly cheaper. The eZoom sells for $99.99, and its monthly plan is $19.99. If you pay for two years at once, you can bring the price down to $12.99 a month.

Securus also makes a couple of GPS devices for other uses. The eCare is meant for seniors who need medical help. In addition to tracking, it has an SOS button that initiates a voice call to an emergency call center. The eCare sells for $99.99, with a $29.99-a-month service plan. Finally, there’s Securus’s dog tracker, called SpotLite, a water-resistant, two-ounce module that hooks on your pet’s collar. (The company says the device is best for dogs weighing more than 10 pounds; it’s not recommended for cats because of its size.)

Then there is a GPS device designed for keeping track of your most important possession: yourself. The SPOT Satellite GPS Messenger, which sells for $119.99 and requires a $99-a-year contract, is meant for adventurous types who routinely wander far off the grid.

If you find yourself in an emergency in a place without any cellphone connectivity, you can hit a button on the SPOT to alert rescuers to your location; the device works almost anywhere in the world as long as you have a clear view of the sky. If you’re not in trouble, you can use the SPOT to send a message letting your friends know you’re fine. They can also track your progress across the Outback on a map. The SPOT has led to dozens of rescues, including of two people whose plane crashed into the Gulf of Mexico early in October.

This article has been revised to reflect the following correction:

Correction: October 22, 2012

An earlier version of this article incorrectly stated the name of the chief executive of Securus. His name is Chris Newton, not Newtown.