Google Pay isn't the only mobile payment service that's gaining support for transit in New York City.
Apple Pay and Samsung Pay work with MTA transit in NYC starting today, May 31st. As noted by The Verge, Apple Pay users will need iOS 12.3 or watchOS 5.2.1 as well as an authenticated debit card or credit card to use the new Express Transit feature. Once you've got those things, you'll be able to use your phone with MTA without having to open an app or even unlock your phone.
Meanwhile, Samsung Pay users will need a Samsung Pay-enabled device. Those include the Galaxy S6 and later as well as wearables like the Gear S2, Gear S3, Gear Fit2, Gear Sport, Galaxy Watch, and Galaxy Watch Active.
Support for Apple Pay, Google Pay, and Samsung Pay is rolling out as part of the MTA's new One Metro New York (OMNY) initiative. Because it's currently being piloted, you can only use your phone or watch to pay your fare on the 4/5/6 subway lines between Grand Central Station in Manhattan and Atlantic Avenue-Barclays Center in Brooklyn and the buses in Staten Island.
Also of note is that these digital wallets are currently only available on a pay-per-ride basis until every subway station, bus route, and Staten Island Railway gets the OMNY technology.
The big draw of Apple, Google, and Samsung's digital wallets is that they can help lighten your wallet's load and maybe one day completely replace it. Lots of folks use public transit every day to get around, and so the MTA adopting support for Apple Pay, Google Pay, and Samsung Pay for their subways and buses is a big deal that'll make it easier for lots of people to get around and avoid having to carry around physical fare.