Starbucks on Wednesday announced the national rollout of a mobile payment system that works with iPhones, iPod touches and select BlackBerry devices. The system works at 6,800 company-operated Starbucks locations and more than 1,000 Starbucks located in Target stores throughout the US.

[ad#Google Adsense 300×250 in story]It’s designed to speed the process of paying for your order, according to Starbucks. It works via a free app you can download through the App Store; the app is tied to the Starbucks Card many Starbucks patrons use to pay for their coffee.

The system has been test-marketed in Seattle, Northern California, New York and in Starbucks at Target stores. Now it’s ready for nationwide deployment, Starbucks reports.

Starbucks reports that more than one-third of their US customers use a smartphone, the majority of which are iOS or BlackBerry devices (an Android app is also on the way, though no release date was announced). What’s more, 20 percent of Starbucks transactions are made using a Starbucks Card. As many of those customers use their phones in line, combining the two systems seemed like a natural for the company.

The process works by generating a barcode on your mobile device’s screen that’s read by a scanner on the countertop.