Kmart, part of Sears Holdings Corp., is one of the chains that have signed up for "ShopAlerts by AT&T." That means AT&T could send discount offers to subscribers who are close to a Kmart store.

AT&T is only able to locate its subscribers to within a mile or so, so its ability to sense that subscribers are in a receptive mood for the offer — like when they’re heading to shop — is limited. The service locates subscribers based on which cell towers communicate with their phones, rather than using the more accurate Global Positioning System chips that many phones have. This means ShopAlerts will work with any phone, not just smart phones that can run third-party applications.

JetBlue Airways Corp. is another participant in the program and could use AT&T’s service to send promotions when passengers are approaching an airport. Other participants are Hewlett-Packard Co., SC Johnson, Kibbles ‘n Bits, Nature’s Recipe and the "Got Milk?" campaign.

AT&T subscribers who want to get the ads need to sign up on the company’s website. For now, they won’t have an option to choose what type of offers to receive, according to AT&T. According to the service, subscribers will get a maximum of four messages per week.

Sending ads to phones based on their location is a long-held dream of retailers, but the technology has been slow to emerge. It’s difficult to tap into the GPS chips of phones, because they drain battery life. Some companies that provide location-oriented apps do sell ads.

In August, a startup called Shopkick Inc. announced a program with big retailers such as Macy’s Inc. and Best Buy Inc. to provide customers with coupons when they "check in" to a store by firing up an app on their smart phone, which senses a short-range inaudible signal specific to each store.

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Online:

http://www.att.com/shopalerts