The HiPay iOS SDK by HiPay interacts with the API to access payments' features that can be integrated into a mobile application. The repository contains the SDK as well as a demo application with a simple payment screen.
Square now has an E-commerce API that brings Square services to third party websites. Square is usually associated with its mobile credit card reader and complementary software. With the E-commerce API, merchants can use their own systems with all the benefit of Square's modern payment services.