Google has announced plans to make its Google Assistant.the voice controlled assistant that has previously been exclusive to the Google Pixel phone, will start rolling out to more handsets from this week., those with other Android Nougat  and  Android Marshmallow devices 
Google Assistant is an overhaul for Google's existing voice-activated phone helper, replacing some of the functions that "Now on Tap" currently offers Android users.The biggest addition is smart home control – Google Assistant can interface with Internet of Things products, letting you speak to your phone to control everything from a thermostat to a lightbulb.

Google Assistant can be switched on with an easy long-press of the home button. No more hunting around for a microphone button on your homescreen.