The New York Times: “Imagine you are shopping in your favorite grocery store. As you approach the dairy aisle, you are sent a push notification in your phone: “10 percent off your favorite yogurt! Click here to redeem your coupon.” You considered buying yogurt on your last trip to the store, but you decided against it. How did your phone know? Your smartphone was tracking you. The grocery store got your location data and paid a shadowy group of marketers to use that information to target you with ads. Recent reports have noted how companies use data gathered from cell towers, ambient Wi-Fi, and GPS. But the location data industry has a much more precise, and unobtrusive, tool: Bluetooth beacons. These beacons are small, inobtrusive electronic devices that are hidden throughout the grocery store; an app on your phone that communicates with them informed the company not only that you had entered the building, but that you had lingered for two minutes in front of the low-fat Chobanis…

…To protect yourself from beacons in the short term, you can delete any apps that may be spying on you — including apps from retailers — and shut off location services and Bluetooth where they are not needed. You can also follow The Times’s guide on how to stop apps from tracking your location. For Android users, the F-Droid app store hosts free and open- source apps that do not spy on users with hidden trackers…”