Associated Press

NEW YORK — Imagine walking by a Starbucks in an unfamiliar city. Your cell phone rings, and a coupon for coffee pops up on its screen, good only at that location.

How did your phone know you were near that particular Starbucks?

Enter location tracking, coming to a mobile device near you. Features that one day will pinpoint your whereabouts to within the length of a football field raise enormous privacy concerns, but they also offer enormous benefits.

The challenge will be determining where to draw the line.

Consider a technology unveiled Monday. Called Digital Angel, a microchip worn close to the body promises to record a person’s biological parameters and send distress signals during medical emergencies.

But misused, these types of capabilities could amount to virtual stalking.

Cell phones, handheld devices, even car navigation systems will soon have detailed tracking abilities, if they do not already.

Much of the drive will come from a federal law that requires cell phones to identify caller locations to speed 911 emergency responses.

"There’s going to be a dramatic increase in the amount of tracking that’s made possible in part by services" consumers don’t even know they have, said Daniel Weitzner of the World Wide Web Consortium, which sets technical standards for the Web.

Such tracking will let someone visit a Web site and automatically get weather, movie showings or neighborhood restaurants, based on their location. If they’re lost, they will be able to ask for directions

But if the information is stored, location tracking could result in a 24-hour-a-day record of a person’s whereabouts.

So what if a divorce lawyer wants to check if someone’s been cheating?

"You have to ask, ‘Who gets how much information?’ " said Jason Catlett, chief executive of Junkbusters Corp., a nonprofit privacy monitoring group in Green Brook, N.J. "Telephone records are routinely subpoenaed. They can be very intrusive, but far more intrusive is a complete log of your physical movement."

Companies looking to gain business from location tracking insist that the worst-case scenarios presented are impractical.

"There’s no way a database is large enough or cost-effective for Starbucks to monitor everyone’s location on the off chance they can acquire a customer," said Jason Devitt, chief executive of Vindigo, which offers 11 city guides through Palm organizers.

Leading wireless and advertising companies agree that they must tread carefully because mobile devices are inherently more personal than desktop computers.

At DoubleClick Inc., whose ad-targeting system has generated many of the Net’s privacy complaints, officials won’t deliver location-based ads right away. The company wants to develop privacy standards first, using lessons from the desktop.

"We’ve all learned what to do and what not to do, and we can port that over to the wireless market," said Jamie Byrne at DoubleClick.

Any such ads will likely target a metropolitan region rather than a city block, because audiences for block-by-block ads would be too small, Byrne said.

In many ways, a person’s whereabouts are already being tracked. Employee security cards record when people enter buildings. Discount grocery programs track what people buy, where and when.

Palm VII organizers could already narrow a user to a particular ZIP code, and an optional global-positioning receiver can pinpoint that person even further.

Paul Reddick, vice president of product management and development with Sprint PCS, said storing such information is not practical, necessary or even desirable.

"It takes years to build a brand and build trust," he said, "and you can blow it pretty fast."

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