From their site: The Presdo API provides a very simple way for web developers to create integrations with Presdo and their favorite web services, applications and even mobile devices. With the API, web developers can create Presdo events through a programmatic interface. The API allows you to specify all the details of an event, such as the time or possible times, guests, location and description. After an event is created, notifications can even be sent automatically to guests. Event participants can then use all of Presdo's capabilities to negotiate the final details of the event.