Time is of the essence in mobile commerce. Mobile shoppers are not kicking back browsing the web—typically they’re looking for something, and want it fast.

Walgreen Co. is wasting no time in getting to a subset of its shoppers. Consumers who check in at a Walgreens store via the foursquare mobile social network instantly receive a coupon for a special offer. What’s more, the coupon can be scanned directly from the smartphone, mobile functionality that puts Walgreens far ahead of the pack.

“We’re using mobile technology and social media to better engage Walgreens customers, to give them convenient channels to interact with us, and to deliver products, services and savings they truly value,” says Sona Chawla, Walgreens president of e-commerce. “Foursquare shares our commitment to innovation and together we’ve developed some unique, breakthrough offerings that cater to today’s tech-savvy consumers. With this program, it’s just check in and the coupon is displayed instantly.”

The Walgreens/foursquare program is an example of the burgeoning SoLoMo technique in mobile commerce: social, local and mobile. The combination of these three ways in which people shop, experts say, can be a potent force.

What is particularly innovative about the program is the method by which coupons can be redeemed. Conventional laser scanners at the point of sale cannot read bar codes displayed on smartphones because the laser bounces off the glass screen. Optical scanners, however, can read codes on smartphone screens. But only a handful of major retailers have installed optical scanners in their stores. Walgreens, No. 42 in the Internet Retailer Mobile Commerce Top 300, late last year installed the new scanners in all of its 7,800 stores.

The first coupon offering, available through March 10, is for 50% off all varieties of AriZona Iced Tea cans.