Jeannie (Voice Actions) is a virtual assistant with over three million downloads, now also available via API.
The objective of this service is to provide you and your robot with the smartest response to any natural language question, just like Siri.
Jeannie API provides an interface to the standard functions that users demand of modern voice assistants, like chatting, controlling your devices, looking up information, creating messages and much much more.
You can extend this API to your own needs.
It also provides useful metadata such as sentence analysis and entity extraction that goes beyond simple chatting and voice commands.
Several million users have already been in contact with this API: http://www.voice-actions.com/