Better hope your battery never goes out, or the network, or the power at the store to power the device you send info to. You'll still need a wallet for I.D./DL.
Retina eye scan and a DNA prick.
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Personally, I'm not a fan at all of using NFC as a means for mobile payments. With as much consumer debt as people carry these days I would personally like to see us getting away from using methods that make it easier for people to pile up debt.
NFC does not equal credit. You can use it for prepaid options as well. Metro tap cards are one example.