See my recent Quora answer to: Which is the best siri like app for android?
>>There are basically two kinds of apps here: apps that will talk with you, and apps that will do things for you (so called “do-engines”). Maybe three kinds if you count apps that do both. Some people are trying to refer to these personal assistant apps as “answer devices” (http://answerdevices.com/).<<
In terms of do-engines, in the beginning there were IRC bots, often erroneously referred to as “chatbots”; natural language commands do not a chatbot make.
Probably Google Now came first with the ambient push, then MindMeld came next with natural language anticipative contextualization, and the newcomer on this block may be Kimera Systems (@kimerasystems) Strong AI (artificial intelligence) by Mounir Shita .