Apple Watch owners in the U.S. can register their Visa, MasterCard, American Express, and Discover (this fall) cards with Apple Pay and initiate payments at the point of sale and in certain mobile apps. Once they activate cards on their watch, users pay by double-clicking the side button on the watch and placing it near a payment terminal’s NFC reader. Apple Pay was launched with iPhone 6 and 6 Plus smartphones. However, consumers can activate Apple Pay on a watch without having Apple Pay on their phone. Consumers using iPhone 5, 5s, and 5c smartphones can buy Apple Watches and registe...