ShopAlerts uses the GPS on your device to detect nearby retail locations. Using a GPS perimeter around the store, ShopAlerts figures out when you're probably entering the store anyway, and will text you relevant coupons.
This differs from other location-based ads/coupons. Some depend on you to check in at a certain location, and others just send you random offers based on your preferences. ShopAlerts is great because the ads are still automatic, but they're appropriately targeted as well.
Some of their participating retailers include HP, Kmart, JetBlue, SC Johnson, Kibbles 'n' Bits, and Nature's Recipe. Those retailers will offer exclusive discounts to AT&T's ShopAlert subscribers. In their initial rollout, it's available in San Francisco, Chicago, Los Angeles, and New York City. More advertisers and retailers are on the way.
source: AT&T via Electronista