This document, which dates back to June of 2004 describes a method of using Bluetooth sensors to find a users location and send ads based on that information. The figure below is taken from the document linked above.
FourSquare has a "Specials" feature, which will display businesses offering discounts near you on a map. It was discussed in this press release on 3/9/11: http://blog.foursquare.com/2011/03/09/a-whole-new-world-of-specials/
Regarding sporting goods, the post also specifically mention Sports Authority running a special through the program.