The touch-screen devices are on display at the Food Marketing Institute's convention here this week.

"It's the utility of being able to create value and get you around the store quicker," said Michael Alexandor, spokesman for Springboard Retail Networks Inc., which makes a smart cart computer called the Concierge.

Canadian stores will test the Concierge in June and July. A competing device, IBM's "shopping buddy," has been test-marketed at Stop & Shop stores in Massachusetts and is being rolled out this summer.

Neither device tells you how many fat grams or calories are in your cart, but they will flash you with items on sale. The idea is to make it easier for consumers to buy, not to induce second thoughts that maybe you should put something back on the shelf.

"The whole model is driven by advertisers' need to get in front of consumers," Alexandor said. "They're not watching 30-second TV ads anymore."

People can use a home computer to make their shopping lists. Once at the store, a shopper can use a preferred customer card, or a key that fits on a key chain, to log into a system that will organize the trip through the aisles.

If you're looking for toothpicks, you type in the word or pick it from a list, and the screen will display a map showing where you are and where you can find them.

The Concierge and IBM's cart are equipped with a miniature equivalent of GPS, the global positioning satellite system. Sensors can track the devices to see right where your cart is, so that as you turn into an aisle, the screen can show what's there and which items are on sale.

The systems also keep a running tally of what you buy. Many stores do so already by signing shoppers up for preferred customer cards. What's new is that the store can offer special discounts based on your buying habits or tell you while you're in the store that one of your favorite products is on sale.

You scan the bar codes on items as you drop them into your cart. When you're finished, the device figures out your bill. Then you swipe your card or key and hand it to the cashier or insert it into a self-checkout stand and pay. All that's left is bagging the groceries.

There are differences between the Concierge and the shopping buddy. The Concierge is mounted on the handle of a cart. With the buddy, shoppers get their carts first and then pick up a buddy as they enter the store. It fits into a holder on the cart.

The Concierge has a bar-code scanner on the bottom of the panel, while the buddy has a detachable wand to scan items.

Like self-checkouts, a smart grocery cart is a way to help stores make shopping trips more convenient, which, along with discounts and other incentives, can cultivate loyalty, said Michael Sansolo, senior vice president of FMI.

That's vital in an industry that has very narrow profit margins and intense competition among different types of stores, from supermarkets to supercenters, discount stores, limited assortment stores and warehouse clubs, as well as natural or organic stores and convenience stores.