AT&T has launched a new service that will send customers texts promoting special deals whenever they're near certain stores.

Teaming up with mobile marketer Placecast to deliver the new ShopAlerts service, AT&T says it's the first mobile provider to offer a location-based marketing program designed for mobile consumers.

AT&T subscribers in New York, Los Angeles, Chicago, and San Francisco who sign up for ShopAlerts will get text messages describing special offers, rewards, coupons, and other promotions at nearby participating stores. AT&T said that so far it's signed up Hewlett Packard, Kmart, JetBlue, SC Johnson, Kibbles 'n Bits, Nature's Recipe, and the National Milk Mustache "got milk" Campaign as the initial sponsors to send out their text-based promotions.

Describing the service as a "geo-fence," AT&T said that it will create a virtual area around a specific store, event, or other area in which consumers can receive location-specific promotions. The messages will also include weather forecasts, traffic reports, and details on local shopping areas to help grab people.

As a couple of examples cited by The New York Times, S. C. Johnson will create a geo-fence around Target stores to text shoppers with discounts on its products, while JetBlue is launching a location-based promotion next month at certain airports to help its TrueBlue members earn extra reward points.

Working through its Advanced Ad Solutions group, AT&T is bringing its large base of customers and a relationship with advertisers to the table, while Placecast is kicking in the location-based technology.

"Placecast is excited to work with AT&T to deliver a new generation of opt-in marketing services focused on delivering relevant messages to consumers when they are in a mindset to make a purchase," Placecast CEO Alistair Goodman said in a statement. "Retailers and subscribers alike benefit from messages with tailored offers available nearby, based on their trusted relationship with AT&T."

Opting into ShopAlerts is free, and people can opt out at anytime. AT&'T is promising that customers will receive only the promotions from the advertisers involved in the program, and that the advertisers won't have direct access to subscribers' mobile phone numbers.