Dive summary: 

• Retailers like Timberland and Kenneth Cole are asking shoppers to trade location information for an in-store discount through mobile app Swirl. 
• Swirl is an opt-in mobile app—users without the app are not tracked—that tracks shoppers' locations throughout a store; small circular sensors are placed throughout a store to collect data on how long a shopper lingers in each section.
• The app sends push notifications of specials that users can opt to check out or not; for example, a patron spending ten minutes in shoes may receive a push notification of a discount on a particular brand. 

From the article: 

"'Because it's opt-in…you're receptive to it,' said Ryan Shadrin, VP of retail and digital commerce at Timberland, which is also testing Swirl. "It doesn't feel big brother-ish, he added. 'We see a lot of these technologies come across the windshield.'

The shoe retailer has tested Swirl since May in two stores, one in New York and one in Boston. According to Mr. Shadrin, 72% of offer recipients checked out the offers and 35% redeemed them. Around 750 shoppers have been served Timberland's 20% discount."