App55 is a UK-based online payment service that enables merchants, websites and mobile application developers to offer their customers secure, one-click payments for products or services via any internet-enabled device.
App55 offers a restful API for access to their payment services. Use the API to send requests to the App55 platform in order to manage users, manage cards, and perform transactions. Responses are returned in JSON or JSONP. Authentication is via API key.