AT&T Wednesday kicked-off a free text messaging alert service designed to help retail customers find discounts and promotions at nearby stores.

The service, called AT&T Alerts, works with all AT&T wireless phones except the iPhone 5. The new Apple smartphone will be compatible with the service sometime in the future, an AT&T spokeswoman said.

The opt-in AT&T Alerts service is relies on geo-location technology that sends alerts based on a user's buying preferences to a mobile device. The geo-location technology relies on nearby cell tower signals to find a phone, not the GPS function on a wireless phone, the spokeswoman noted.

AT&T Alerts uses insights the carrier gained from the Shop Alerts program it launched in a few cities last year.

To sign up for the service, AT&T wireless customers must text "JOIN" to ATTAlerts.

Brands involved in the promotions include The Gap, Staples, Zales and Last Call by Neiman Marcus, as well as product makers Duracell, Motorola, and the Discover credit card.

The text messages to and from AT&T are free, and customers signing up will receive $5 off of a minimum $10 purchase at ATT.com, the company said.

Matt Hamblen covers mobile and wireless, smartphones and other handhelds, and wireless networking for Computerworld. Follow Matt on Twitter at @matthamblen, or subscribe to Matt's RSS feed . His e-mail address is mhamblen@computerworld.com.