Most noticeable will be the use of the fingerprint ID sensor to authorize transactions. Right now, it's easy to pull out a plastic credit card, so any mobile-payment system will have to be just as easy. That can't be said when you have to spend time typing in a passcode at the checkout line. The fingerprint ID lets you bypass that with one tap.

Eric Risberg/AP
A cash register terminal promotes usage of the new Apple Pay mobile payment system at a Whole Foods store in Cupertino, Calif. on Oct. 17.