Hopping said a shopping cart could eventually be outfitted to interact with the shelves so a shopper could see an ad or an offer about chicken noodle soup just as he heads into the soup section.

The smart cart raises concerns about privacy for many people. Hopping emphasized that consumers are free not to use a store card and thereby not have their purchases tracked, but he believes they will find that the convenience outweighs the intrusion.

Kathryn Cullen, a technology specialist at Kurt Salmon Associates, a retail consulting firm, said some retailers are shying away from such extensive use of the store card, also known as a "loyalty card."

"This is a very sensitive topic. I may not want the store to be broadcasting what I bought last time I was in here. You're getting closer and closer to being inside my home."

On the other hand, she said, consumers have a history of eventually acceding to such intrusion for the sake of convenience.

"Look at the E-Z Pass," she said. "They know where we're going but we use it to save time."

On the horizon, the consultants say, is the day when every product is tagged with an RFID, or radio frequency identification chip, instead of a bar code. The chips, which don't have to be scanned, would allow shoppers to leave the store without checking out at all and get the bill on their credit card or store account.

There doesn't seem to be any controversy about "Veggie Vision," a scale for fruits and vegetables that is hooked up to a digital camera and a library of hundreds of pictures of produce. When a shopper puts tomatoes on the scale, the machine evaluates their color, texture and shape to determine what they are, then weighs and prices the purchase.

Not only can it tell an apple from a tomato, but unlike some checkout clerks, it can tell a McIntosh apple from a Red Delicious.

The "Everything Display" is a computerized camera and projector that can flash an advertisement, for example, onto a bare wall in the format of a touch screen on a computer. There is no screen, but when a shopper reacts to the ad by touching a spot on the projection, the camera interprets the movement and the projector flashes the appropriate page onto the wall.

"It turns any wall, or even a floor, into an interactive display," said IBM research scientist Tony Levas. "People react as if it were a touch screen. I think they think it is a touch screen."