Apple changed the way you shop for music and movies and audiobooks. Now the tech giant wants to change the way you shop, period, by turning your iPhone or iPad into your new credit or debit card. The Wall Street Journal reports Apple is in the process of building a mobile payments system to compete directly with PayPal, Google and Square. Apple already has the pieces in place to build a mobile payment empire. If these existing functions were to come together, like a technological Voltron, Apple could very easily become a force in mobile payments.