AT&T has partnered with location-based mobile marketing platform Placecast to provide users with ShopAlerts, special offers sent to their mobile phones when they are near a store or brand.

The location-based mobile messaging service will be available for AT&T customers in New York, Los Angeles, Chicago, and San Francisco who have opted-in to receive messages.

The  ShopAlerts will provide users with offers, rewards, and coupons based on their specific geographic location. AT&T creates a "geo-fence" – a virtual-perimeter around a retail location, event, or any geographic area to send appropriate location-specific messages.  Participating consumers receive marketing messages when they are inside a geo-fence.

The initial companies  participating in ShopAlerts include HP, Kmart, JetBlue, SC Johnson, Kibble ‘n Bits Nature’s Recipe and the National Milk Mustache "got milk?" Campaign.

“We are proud to take mobile marketing into the future with this unique offering that is being embraced by consumers and brands alike," said Greg McCastle, senior vice president of AT&T Advanced Ad Solutions.

"ShopAlerts by AT&T enables brands/advertisers to help link consumer engagement with activation and ultimately to the point of sale."