The Starbucks Corp. mobile payment application now lets users track rewards for their coffee purchases.

The software, developed by mFoundry Inc. of Larkspur, Calif., lets users make purchases by loading a bar code on the screen of an Apple Inc. iPhone or iPod Touch and holding it up to a scanner at the point of sale. More than 1,000 Starbucks sites, primarily in Target Corp. stores, can accept the software.

The new loyalty feature lets users track their progress toward earning Starbucks rewards. It ties in to Starbucks' existing rewards program, which offers free drinks and other perks based on users' purchases.

Drew Sievers, mFoundry's co-founder and chief executive, said in an e-mail that the Starbucks application is the largest mobile payments and loyalty program in the U.S., but he would not give specific numbers. Adding the loyalty-tracking feature has attracted many new users to the application, he said.

Starbucks introduced the feature in 16 stores last September. Target started a similar system in February to accept gift card purchases, though it does not use mFoundry's technology. Starbucks then asked mFoundry to adapt its system to be compatible with Target's, allowing the coffee retailer to further expand mobile card acceptance to the more than 1,000 Starbucks sites in Target stores.