15 July 20149to5Mac:
To substitute for a physical gift card, iTunes Pass installs a new pass inside of the iOS Passbook application. The Apple Store employee can scan the pass in order to immediately apply the credit to the Apple account. Users can install the iTunes Pass feature in Passbook on the main screen in the iPhone iTunes Store app. This enhancement is Apple’s second first-party use of Passbook. Apple previously opened up the ability for Apple Store gift cards to be stored in Passbook.
This feels like something Passbook should start with. Everyone with an iOS device has an iTunes account, so everyone can get some form of utility out of this pass. It would stop Passbook from being empty by default.