You use your phone 99.9% of the time, and have a backup card the exact same form factor as a credit card, that you keep with your credit cards and driver's license, for the 0.1% of the time you can't use your phone.

And if you opt for the fob, then you don't need to carry a backup card at all, because even when its battery is dead, you can tap it against the reader just like you would with the card.