Siri

Siri is a virtual assistant application built into certain iOS devices. It hears what the user says and responds by web services. At first, Siri was an app in the App Store, but Apple bought the company that owned it, on April 28, 2010. Siri has been supported by all devices since the iPhone 4S, and is in iOS 5 devices other than the third generation iPad. When iOS 6 came out, the third generation iPad got Siri, as well as the iPhone 5, iPod Touch (5th generation), fourth generation iPad, and iPad Mini. 
A similar system is built into Android (Google Assistant), Samsung () and Windows Phone ().