The iMessage app can be deleted, but, for some reason, can't be re-downloaded anyhow unless the user factory resets the device.
iOS 11.2 is now live and so is Apple Pay Cash, Apple's answer to PayPal within its Siri, iMessage and Apple Pay ecosystems.
The update came out days early to fix a trigger for iPhone and iPad crashes that would have come on December 2. It's still unknown how this bug exists.
Peers can send money to each other through iMessage and use whatever money they put into the system with Apple Pay merchants.
Owners of a large number of "old" iPhones, iPads and even the latest iPod Touch generation can officially update today to the first public iOS 11 build.