Warning: if you remove the Apple Pay Cash app, it's not obvious how to get it back
The Apple Pay Cash 'app' is built in to iOS, so you might well expect that it would be locked in place, completely un-uninstallable. But that's not the case. In fact, you can remove -- or at least hide -- the app, but you will run into problems if you ever change your mind and decide you want it back.
If you are running iOS 11.2 -- which introduced Apple Pay Cash -- you can easily uninstall the app if you feel you don't want it. But there is no obvious way to get it back, meaning that while you can still use Siri to make payments, you won't be able to do so in iMessage. This is something that may well be fixed in iOS 11.3, but in the meantime there are a couple of work arounds.
Apple Pay Cash rolls out to iOS 11.2 users in the US
Over the weekend, Apple pushed out iOS 11.2 a little earlier than planned to address a crashing problems affecting iPhone users. The update included a non-functioning version of Apple Pay Cash, but now Apple is flicking the switch to activate the new payment options.
Apple Pay Cash makes it possible for people to send and receive payments through iMessage. It serves as an alternative to the likes of PayPal, and it's a payment option that's now rolling out across the US, with other parts of the world to follow in due course.