How your cellphone betrays you
How your cellphone betrays you

There’s a traitor in your pocket. Or your purse. Your cellphone is ratting you out. Stores can keep track of who you are and what you buy -- unless you pay cash. Now they can also use your cellphone -- even without your permission -- to find out even what you’re just looking at or trying on. Nordstrom, the high-end department store, began using a technology that can use the Wi-Fi signals in shoppers’ smartphones to follow them virtually throughout the store, from display to display, item to item, and check how long they spent looking at what, just as websites can do now. Nordstrom isn’t the only company trying this out. At least Nordstrom put up a sign to let customers know what it...