RENEE MONTAGNE, host:
There's a good chance that you are right now carrying around a tiny device that's picking up faint radio signals from space and keeping track of your location. It's a global positioning system, or GPS receiver, built into your cell phone. A hundred million or so people in the U.S. have those devices. Few, up to now, have been able to use them.
Dan Charles reports.
DAN CHARLES: Chuck Fletcher in Montclair, New Jersey, is one of those people who think the global positioning system is pretty much the coolest gizmo on the planet.
Mr. CHUCK FLETCHER (Co-creator, Mologogo): GPS is pretty magical technology, actually. I mean just the idea that there are satellites out there floating up in the sky that are put up specifically to help you figure out where you are.
CHARLES: So when Fletcher heard that GPS receivers were showing up in cell phones, he started imagining ways to use them. He and another programmer created some software for cell phones called Mologogo.
When Fletcher pulls out his phone now and selects Mologogo, it displays a map of the streets around him. A dot shows his location. It also shows where Fletcher's friends are, if they have Mologogo running on their cell phones and agreed to share their whereabouts with him.
The phones all transmit their locations to a Web site, so Fletcher also can log in from any computer and find his friends that way.
Mr. FLETCHER: You can search for your friends. You can even kind of set it up to track one friend and you actually, you know, if that's the person you're interested in today because they're doing something interesting, you might want to set it up just to watch them and see where they are and what they're doing.
CHARLES: You can download Mologogo for free, and Fletcher says about 2,000 people have taken the trouble to install it on their phones. One of them left his phone in a taxi by accident one day and then watched it on his computer zooming back and forth across New York City until the cap driver found the phone and called him.
Mr. FLETCHER: There's a lot of people who are using it as a way to just share their travels.
CHARLES: But before you rush to download Mologogo, you should know it won't work on most cell phones, even on most phones equipped with GPS receivers. That's because most companies that sell the phones have locked that information away inside the phone where you can't get at it. Only one company, Nextel, has, from the get-go, allowed people to retrieve geographic coordinates from the GPS chips in its phones.
So Mologogo works on phones from Nextel or Nextel's prepaid service, Boost Mobile, but not on others.
Mr. FLETCHER: Pretty much, if you can't talk to the chip, you're just - you're kind of out of luck.
CHARLES: Several cell phone companies have recently launched services that use the GPS receiver to give you directions or track your kids, but you have to buy those services and they're only available on certain phones.
Don Cooke wishes the companies were moving faster. He's an executive at Tele Atlas, a mapping company. He's also the author of a book called Fun with GPS, which suggests using GPS devices to map your hiking trails or figure out where your dog goes when it disappears for hours on end.
Mr. DON COOKE (Senior Scientist, Tele Atlas; Author, Fun With GPS): A lot of people like me are very frustrated because we can't get at the internal coding of the cell phone to be able to use it.
CHARLES: But Mary Foltz, who's director of wireless data business products for Sprint Nextel, says there are good reasons to keep your whereabouts under wraps.
Ms. MARY FOLTZ (Director of Wireless Data Business Products, Sprint Nextel): Location information is incredibly sensitive and incredibly private.
CHARLES: Cell phone companies originally didn't even want to acquire that information. The government ordered them to so when people called 911 on their cell phones, rescue crews knew where to go.
Ms. FOLTZ: Our number one priority was to absolutely contain that information so that if it's being provided, it's only with the customer's consent and in a way where they have full control of it.
CHARLES: But many in the mapping business say there's another reason apart from privacy concerns why the cell phone companies are keeping such tight control over location information. They're hoping to convert it into profits. Some of the new services now hitting the market show that GPS receivers are good for a lot more than just tracking people.
Mr. BRAD BLUMBERG (CEO, Smarter Agent): We're right behind the Library of Congress at the Folger Museum.
CHARLES: Brad Blumberg, CEO of a company called Smarter Agent, is looking at tiny map of Washington, D.C. displayed on his Sprint cell phone.
Mr. BLUMBERG: And these little blue houses - you see ten blue houses plotted on the screen.
CHARLES: Those are the houses closest to us that sold within the last three years. Blumberg selects one, and more information appears.
Mr. BLUMBERG: That property sold for $850,000, so it is getting a little expensive back here. I remember when this neighborhood was not so expensive.
CHARLES: Smarter Agent is one of the new authorized services that Sprint Nextel customers can buy. Blumberg can walk around any major city in America, look at houses in front of him and find out what they're worth. And in the future it might not be just prices.
Mr. BLUMBERG: What's really dear to my heart is we'd be able to stand here and I'd be able to learn about the architecture of the buildings in front of me. Based on your interest, you'll be able to pick history and all the sudden will come streaming, you know, do you want to know what was here in 1700, 1600; and if it was 1700, maybe we'd send you a picture of the area.
CHARLES: Cell phones could in fact be set up to retrieve any information that's stored in a database somewhere. So you could stand on a corner, get phone numbers of people on that street, the median income of the neighborhood; or if you want to frighten yourself, you could see if any murders were committed nearby. The cell phone could become your guide to things you can't see in the world around you.
For NPR News, I'm Dan Charles.