AT&T Inc. (NYSE: T) claimed Monday that it is the first major U.S. carrier to offer a location-based mobile marketing service aimed at driving consumers to specific retail locations with targeted offers.

The "ShopAlerts" system will provide subscribers -- that opt into the service -- with offers, rewards and coupons based on their specific locations in New York, Los Angeles, Chicago and San Francisco. To provide the alerts, AT&T creates a wireless perimeter around a retail location, event or specific geographic area in order to deliver appropriate location-specific messages. Participating consumers receive relevant marketing messages -- with additional information such as weather, traffic and local shopping-area details -- when they step inside an AT&T "geo-fence".Initial sponsors for the ShopAlert service will be HP Inc. (NYSE: HPQ), Kmart, JetBlue, SC Johnson, Kibbles 'n Bits, Nature's Recipe and the National Milk Mustache "got milk?" campaign.

Why this matters
With this new service, AT&T is combining the capability to target ads very accurately -- because it knows a handset user's location through GPS and other network data -- with the popularity of online city coupon alerts like the popular daily offering from GroupOn.

But just how many AT&T subs in these major metropolitan areas will sign on to let retailers in on their location remains to be seen.

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