"Hey Alexa." "Hey Siri." "Ok Google."Hearing people say these phrases and talk to their smartphones, speakers, and wireless earbuds has become such a common thing that no-one bats an eye when they hear them. Smart assistants used to be a selling point of smartphones. In fact, Apple's Tim Cook said that when the 4S was released, the S was added with Siri in mind. These days, a smart assistant is fast becoming a must-have in all high-end smart devices.