Is any mobile device suitable? Not really. You can use all those compatible with "Google Assistant", which are those that have installed "Android Marshmallow (6.0)" onwards, with more than 1.5 GB of RAM and at least have a screen with HD resolution. It is very easy to verify this compatibility. You must press and hold the Home button for a few seconds and say "Ok, Google". In case the device is compatible, the virtual assistant will automatically activate with which you can start to issue ...