THIS week Apple announced two new pieces of hardware, the iPhone 6 and a “smartwatch.” But as flashy as they are, neither item is as groundbreaking as a piece of software that will accompany them: a digital wallet, allowing users to eschew cash and credit cards for a quick swipe of their device at the register.

Apple’s digital wallet, if widely adopted, could usher in a new era of ease and convenience. But the really exciting part is the fast-emerging future that it points toward, in which virtual assets of all sorts — traditional currencies, but also Bitcoin, airline miles, cellphone minutes — are interchangeable, opening up enormous purchasing power for consumers and creating tough challenges for governments around the world.