As the world's biggest smartphone makers work to improve indoor location-based services for consumers, retailers are already using various techniques to track customers in a bid to gain an edge on their online competitors. The New York Times reports that brick and mortar stores are following Wi-Fi signals from customer smartphones to gain information on their sex, the amount of time they spend in parts of the store, and how long they browse before they buy. While web stores like Amazon use cookies to track website visitors, traditional retailers have to rely on video systems (capable of differentiating age and gender) and radio technologies to monitor customers — something that unnerves those worried about privacy. Despite this, numerous companies are coming up with new and covert ways to help retailers find out more about their customers, allowing them to tune store layouts, offer discount coupons, or reward frequent buyers, much like their online counterparts.