The iPhone 5S will likely feature biometric security via fingerprint sensor, reports indicate, though this functionality is unlikely to play a role in payments. However, if the sensor works for more than just unlocking the phone, such as logging into merchant sites or iTunes, it could play a powerful role in mobile commerce.

Less certain is the state of NFC in the iPhone 5S and its cheaper cousin in the plastic case, the 5C. (The “S” is rumored to stand for security – would that make the “C” cheap?)

NFC, or near-field communication, has long been held out as a promising technology for mobile commerce, but it has yet to deliver. Its lack of inclusion on the iPhone 5 was seen a serious blow to NFC’s chances for widespread adoption.

But if both features show up at tomorrow’s event, in tandem they make for a solid mobile wallet. Users could tap the button and be simultaneously authenticated and authorize a payment to a nearby terminal. Would that mean changes are also in store for Apple‘s neglected Passbook app?

The plastic of the iPhone 5C housing makes it a better use case for an internal NFC component for payments, but it is unlikely that Apple would leave a feature as prominent as NFC off the flagship 5S. The NFC functionality will be driven, it appears, from the home button, as will the fingerprint sensor. (The home button already has many uses.)

A patent filed by Apple in Europe details the possible biometric and NFC features of the new button.