Like dozens of other brick-and-mortar retailers, Nordstrom wanted to learn more about its customers - how many came through the doors, how many were repeat visitors - the kind of information that e-commerce sites like Amazon have in spades. So last autumn the company tested technology that allowed it to track customers' movements by following the Wi-Fi signals from their smartphones.

But when Nordstrom posted a sign about it, shoppers were unnerved.

Nordstrom ended the experiment in May, in part because of complaints, a spokeswoman said.

Nordstrom's experiment is part of a movement by retailers to gather data about shoppers by using video surveillance and signals from their cellphones and apps.

"Way over the line," one consumer posted to Facebook in response to a news story about Nordstrom's efforts.

Physical retailers argue that they are doing nothing more than what is routinely done online.

"Brick-and-mortar stores have been disadvantaged compared with online retailers, which get people's digital crumbs," said Guido Jouret, the head of Cisco's emerging technologies group, which supplies tracking cameras to stores.

"The idea that you're being stalked in a store is, I think, a bit creepy, as opposed to, it's only a cookie - they don't really know who I am," said Robert Plant, a computer information systems professor at the University of Miami School of Business Administration.

The companies that provide this technology offer a wide range of services. RetailNext, of San Jose, California, uses video to study how shoppers navigate. It differentiates men from women, and children from adults.

RetailNext adds data from shoppers' smartphones to deduce even more specific patterns. If a shopper's phone is set to look for Wi-Fi networks, a store that offers Wi-Fi can pinpoint where the shopper is in the store, within three meters, even if the shopper does not connect to the network, said Tim Callan, RetailNext's chief marketing officer.

The store can also recognize returning shoppers, because mobile devices send unique identification codes when they search for networks.

Brickstream, based near Atlanta, Georgia, sells a $1,500 stereoscopic camera that separates adults from children, and counts people in different parts of a store to determine which aisles are popular and how many cash registers to open.

Realeyes, based in London, analyzes facial cues for responses to online ads, monitors shoppers' so-called happiness levels in stores and their reactions at the register. Synqera, a start-up in St. Petersburg, Russia, is selling software for checkout devices or computers that tailors marketing messages to a customer's gender, age and mood, measured by facial recognition.

"If you are an angry man of 30, and it is Friday evening, it may offer you a bottle of whiskey," said Ekaterina Savchenko, the company's head of marketing.

Nomi, of New York, uses Wi-Fi to track customers' behavior in a store, but goes one step further by matching a phone with an individual.

When a shopper has volunteered some personal information, either by downloading a retailer's app or providing an e-mail address when using in-store Wi-Fi, Nomi pulls up a profile of that customer - the number of recent visits, what products that customer was looking at on the Web site last night, purchase history.

Nomi then follows the customer throughout the store, offering coupons for products the customer seems especially interested in.

At least some consumers seem happy to trade privacy for deals.

"I would just love it if a coupon pops up on my phone," said Linda Vertlieb, 30, a blogger in Philadelphia, who said that she was not aware of the tracking methods, but that the idea did not bother her. Stores are "trying to sell, so that makes sense," she said.

The New York Times

(China Daily 07/28/2013 page10)