Send a Friend Money With Your Apple Watch
Once you install the free watchOS 4.2 update you can send cash or ask for cash from your Apple Watch using Apple Pay Cash.
Apple Pay Cash is a new service from Apple that lets you send money from a debit card to someone else who has an iPhone or Apple Watch and when you get money you can transfer the money to your bank or use it like a credit card.
You'll need to setup Apple Pay Cash on your iPhone to start using this service, but once that is done you can quickly send money. Open up a message on the Apple Watch and then scroll down until you see the Apple Pay option. Tap on it and then choose an amount.