In parts of the world like London and Tokyo, NFC-powered payment cards can be used to pay for public transit. They're so popular in Taipei that other businesses like convenience stores began accepting them as a form of payment, and the cards have been made in an endless assortment of shapes.
Reimagining the card — Since the cards are just a piece of plastic with an NFC chip inside, and you're not doing any swiping, there's no reason they need to come in a traditional plastic card shape. You could, for instance, put an NFC chip inside a Poké Ball and use that to pay. So the company that makes Taipei's transit cards, EasyCard, made just that in a partnership with Niantic. The thing even lights up when your purchase has gone through.
The Poké Ball EasyCard went on sale in Taipei last year with a limited run of 3,000 units, and it sold out almost immediately. The company sold out of another 14,000 and is now planning to bring them back again this year. The last version was priced at $11, so expect it to cost about the same when it goes on sale around mid-October.
Benefits of NFC — Similar contactless public transit cards exist in the U.S., but because Taiwan's implementation uses the NFC standard found in most credit card readers, the EasyCards can be used in vastly more places. Since 2010, EasyCard has expanded the number of merchants that can accept its cards to over 10,000 outlets.
Using EasyCards to pay for goods is safer than a credit card because, since these were designed as transit cards first, they have limited balances and have to be manually reloaded with more value. Somebody can't drain your bank account if they get ahold of your Poké Ball.
Another benefit of public transit systems using NFC is that riders can pay without a transit card at all. In London for instance, riders can pay their fare with Apple Pay, Google Pay, or any credit card that has an NFC chip inside.
New York City is slowly rolling out this type of system across the MTA and it will be offering a prepaid card similar to EasyPay. Who knows, maybe Americans will someday be able to pay with Poké Balls? With how slowly infrastructure projects move in this country, though, I wouldn't get your hopes up.