VoipNow currently offers 3 Services, each of them with a different purpose. As a developer, you may interact with one or several of them, depending on your application:

This REST based API allows you to manage extensions phone calls in real-time, gather information about history calls, send faxes, etc.

Call Events
A service that provides methods for notifying a third-party application when phone calls are coming or leaving the system.

Call Interactive
This service can be used with IVR extensions and allows third-party applications to control the call flow in the IVR by means of XML actions.