Hospital leaders at a meeting there are wearing nTAGs, devices that elevate the lowly name tag to an astonishing-but-slightly-creepy-social-networking tool.

When you're wearing an nTAG, you and a fellow conventiongoer can exchange virtual business cards by holding your nTAGs close and pushing a button. Blue lights flash the news of your union. You can check your personalized agenda, vote electronically, make notes about your new friends, take tests, and learn who won the raffle.

The 4.5-ounce, rectangular gadgets, which are worn on a lanyard like their paper-and-plastic predecessors, can be set to vibrate as you near a coveted business prospect and flash his or her photo so you can move in for the conquest. Unless your prey foils you by "cloaking."

Maybe not so enticing, nTAGs, which are making their first appearance in Philadelphia, also make it a little harder to skip that session on supply-chain management to check out the cheesesteaks at Reading Terminal Market.

The nTAG can make a record for your boss of where you spent your time and with whom you spent it. (The folks at VHA Inc., the sponsors of this week's convention, say they're not using it that way.) In real time, event organizers can tell which vendors are drawing a crowd and which speakers were duds.

For those of you wondering how useful divorce lawyers might find these records, nTAGs work only within the confines of the convention center.

Nonetheless, privacy expert Mark Rotenberg, executive director of the Electronic Privacy Information Center, has concerns.

"It's information that's being collected about you, and you don't really have any control about how it's being used," Rotenberg said. The ethics of tracking the whereabouts and contacts of travelers, employees and federal workers with devices like this is a hot topic in Washington now, he said.

The interactive name tags seem benign enough in a company meeting, Rotenberg said, but that doesn't mean the data they collect won't someday find their way into hostile hands. "You almost have to assume, with most of these implementations over time, that just about anything that can be done will be done," he said.

Mark Borovoy helped develop nTAGs as a "high-tech ice-breaker," while working on his doctorate at MIT. He is now chief technology officer for nTAG Interactive Corp., the privately held company that markets the devices. He said no lawyers or detectives, since the company launched the product in 2002, have asked for a meetinggoer's records.

Your boss won't get the details of your visit unless you hand it over, Borovoy said. People are always told how much information will be disclosed before a meeting starts. Most find the devices so useful that they don't worry about it, he said.

And besides, people already willingly give up a lot of personal information in exchange for use of their cell phones, credit cards and grocery store cards.

"You're living in a networked world," Borovoy said.

So networked, in fact, that he could tell from his office in Boston yesterday that the 2,800 people registered for the VHA meeting had exchanged 29,000 virtual cards by 11:15 a.m. The meeting of the Texas-based hospital organization started Saturday and will end today.

Sandra Lindstrom, VHA's senior director of conference and meeting services, said nTAGs, which employ a combination of radio-frequency and infrared technology, fit the meeting's theme: The Power of Innovation. The meeting is for health-care leaders interested in purchasing and quality improvement.

"It's new. It's different. It's sexy. It's fun, especially for people who like to play with gadgets," said Lindstrom, who is something of a trend-spotter. Brightly colored charms dangled from her cell phone. They're hot in Japan, she said.

At $15 to $20 per person per day, nTAGs aren't cheap. VHA went green this year, forgoing paper agendas for fully electronic versions, and used the money it saved on the name tags. Was it worth it?

"I'll tell you later," Lindstrom said.

Over the last year, conventions in Philadelphia have started using interactive devices for voting in sessions or recording vendor contacts, said Jack Ferguson, executive vice president of the Philadelphia Convention and Visitors Bureau. NTAGs are the most complicated so far.

VHA this week used the nTAGs in part to drive traffic to vendors. Attendees got points toward high-tech prizes for exchanging information at the booths.

Hospital leaders and vendors said the devices made it easier to exchange information and to keep track of their schedules.

"This is really neat," said Cindy Quint, a nurse manager at Underwood Memorial Hospital in Woodbury. "It tells you everything." By midday yesterday, she had met 44 people and exchanged virtual cards with 23 of them.

She had no intention of skimping on work, so she didn't mind the record of her whereabouts. "It's to my advantage that I make sure that I attend these sessions," she said, "because there's a lot to be learned here."

Donna Cochran, director of nursing, cardiac and emergency service at Jameson Hospital in New Castle, Pa., said she believed the record of seminars and contacts would be helpful. "Facilities don't send you here just to give you a day out," she said as she finished lunch with two coworkers. "Each of us will have to go back and give a presentation."