When you look at your smartphone, you probably don’t spend much time thinking about the poor calculator, day planner and digital camera it helped send to the dustbin of history. But starting today, that same phone is taking aim at another victim: your wallet and the credit cards you carry in it. Both are on “deathwatch” as Apple rolls out Apple Pay for the iPhone 6 and 6 Plus. While the impact of the new software will be limited at first, it will usher in a new era of convenience and security that will ultimately bring benefits to everyone — whether or not they are iPhone users. Here’s what you need to know.