Perhaps the most popular activity in mobile commerce is researching products and comparing prices on a smartphone while in a store. Consumers want the power of an e-commerce site in a mobile-optimized version that fits in the palm of their hands to ensure they know what they’re buying and get the best deal. So what’s a retailer to do to keep consumers in its store when shoppers are armed with these powerful mobile devices that could lead them elsewhere?

San Francisco Bay Area Verizon Wireless dealer EVO2 is encouraging shoppers to use their smartphones—not to compare prices, but instead to get a free phone. A shopper uses her old smartphone to scan a two-dimensional bar code on the door of an EVO2 store to lead to mobile web-based promotional content they then post on her Facebook page. Once an EVO2 representative confirms the post, the shopper can choose any phone (excluding the iPhone) in-store for free, with a 2-year wireless plan activation, and after a mail-in-rebate.

A two-dimensional bar code appears as a square with an abstract image, most commonly black and white. It can contain much more information than the common one-dimensional bar code that appears on all consumer packaged goods. It can also connect a shopper to any kind of mobile web content, such as contest forms or product videos. EVO2 is using a type of 2-D bar code known as QR, or Quick Response. A consumer must download a free 2-D bar code reader—there are many in app stores—onto her smartphone to scan codes.

The promotion, which runs through June 30, is designed to get more consumers signed up for a wireless contract with Verizon. Wireless carriers, mobile experts say, make far more money on monthly wireless data plan fees than they do on mobile device sales.

“That’s an offer that’s worth hundreds of dollars,” says Robert Marhamat, vice president of sales at EVO2. “Plus, if you bring in a friend and each of you takes advantage of the promotion, both of you will receive a $25 referral card.”

Marhamat adds he expects popular phones such as the Samsung Charge, Droid Incredible 2, HTC Thunderbolt, HTC Trophy, Droid X, BlackBerry and Droid Global models to be going quickly.