We are glad to announce that Square now supports Tap to Pay on iPhone as a payment acceptance method in POS API for sellers in the US. Tap to Pay on iPhone allows sellers to accept contactless payments using only an iPhone, with no external hardware required. The buyer holds a contactless card or a mobile wallet over the seller’s iPhone to complete the transaction.
Sellers using the POS API within their app, and who have updated their iOS Square Point of Sale app to v6.0, will have the option to enable Tap to Pay on iPhone directly in Square POS via Settings. We are informing you about this new feature in case you start seeing Tap to Pay on iPhone payments flow through. Check out our website for more info and feel free to ask any questions in this forum!
At this time Tap to Pay only works with the Square app. So integrating it into your own custom app isn’t currently available. Also we don’t have public roadmaps for feature requests like this.
So as per Apple they are providing ProximityReader so:
Your app uses the ProximityReader framework to read the payment method someone presents. You then pass that payment method and transaction details to the payment service provider you use to handle financial transactions.