Apple Pay Cash is now up and running5
The good news is that the gang in Cupertino have now flicked the switch turning on Apple Pay Cash. To begin using the feature, you need to go to Apple Wallet, tap on Apple Pay Cash, and follow the routine to add a debit card. If you use a credit card, there is a 3% fee on each transaction, which can be avoided altogether by using a debit card. If you're using a debit card for Apple Pay, iOS 11.2 will recommend that you use the same one for Apple Pay Cash.
Apple Pay Cash allows for peer-to-peer money transfers over the iMessage app. Both parties to the transaction must have it enabled on their iPhone or Apple Watch. A balance in Apple Pay Cash can be transferred to a connected bank account and can also be used to pay for transactions inside stores or online using Apple Pay. You can ask Siri to make a payment by saying something like "Apple Pay 25 dollars to Mary for dinner" or "Send 25 dollars to Mary."
To see a demonstration of Apple Pay Cash in action on an iPhone, click on this link.