Apple Pay Cash lets US-based users send and receive money through iMessage, with funds drawn from a linked credit or debit card. Watch users can tap the new button at the bottom of an iMessage conversation to initiate a payment to that contact. The update also adds support for HomeKit sprinklers and faucets and improved snow sports tracking for third-party apps running on an Apple Watch Series 3. WatchOS 4.2 will only work when the wearable is paired with an iPhone running iOS 11.2.”]
Source: https://arstechnica.com/gadgets/2017/12/apple-pay-cash-hits-apple-watches-with-watchos-4-2-release/