TL;DR
You can easily extend your custom checkout with loyalty functions for gift cards or bonus cards:
You need to pass a device code and the card number to the Smart Transaction.
You can charge cash balance or collect bonus balance, spend the card balance, or request an instant discount.
You can also create a new card, and already use it with the current order.
Our secuconnect SDKs for JavaScript, PHP and Java help you with coding.