Video: How Stores Like Nordstrom Track You Via Your Smartphone's Wi-Fi Signal

Privacy advocates have an entirely new worry to keep them awake at night. National retailers like Nordstrom and Home Depot, working with a company called Euclid Analytics, have devised a method for tracking shoppers in their stores. The service identifies shoppers' smartphones by requests the devices make for Wi-Fi, even if they aren't connecting to the store's network.