Compare it with Starbucks Mobile App - can you see any similarity? (No, I have never sent this proposal to Starbucks... Unfortunately... )
However, there is a big difference as well: in my solution, the card number was not displayed on the mobile phone screen as it is done in Starbucks app (xxxxxxxxxxxx9189 in the screenshot below). My app was displaying just 4 digits - simple randomly generated token (4067 in the screenshot below) which becomes useless as soon as the barcode is scanned (or the 4 digits are keyed) by cashier and the mobile device is linked with the point of sale transaction. The actual payment card number was never exposed to the mobile device and point of sale because the transaction was processed in a cloud between mobile app and point of sale servers.