Starbucks mobile payment application for iPhone, iPad and iPod Touch is expanding (reports ReadWriteWeb). Not only is it going to be available on for Blackberry, but after the successful field test in the San Francisco Bay Area, its spreading out and will be available in 6,800 Starbucks stores and around 1,000 franchises in Target stores across the US.

The app ties in to the physical Starbucks Cards, which now account for 20% of all payments made in-store. Like many retailers, the Coffee Company have managed to get a working card payment system into the minds of their customers, customers who trust not only the brand, but their Starbucks card. Now they’re transitioning this loyalty into a fully electronic system.

It’s one less thing to carry in their wallet, and there’s a futuristic thrill to paying with a swipe of your phone. And unlike all the hardware that Google have placed in the latest phones or third party hardware hacks, Starbucks’ app just pops up a barcode on your smartphone’s screen for the cashier to scan.

You can be sure that Starbucks are going to incentivize the switch from the existing card to the application, just as they pushed benefits to the card over cash in the stores (with simple twist such as free flavoured syrup and extra espressos shots if you used the card), but this is going to be an exercise with the warm-up already done.

Starbucks have loyal card users, happy to deposit money, that trust the system and know it has benefits for them. Exactly the sort of messages that any mobile money system would love to have.

You might disagree with how their coffee tastes, but their methods in rolling out their payment system are certainly worth studying… maybe over a double shot latte with some caramel syrup.