Call Someone Hands-Free Using Google Now Command
You can do a lot of cool things with your voice on your phone, but did you know you can make phone calls too? Pretty neat. Google Now can even initiate hands-free calls directly with a voice command.
To make a speakerphone call, simply say “Call [the person] on the speakerphone.” Google Now will recognize that it should start a hands-free call. This is especially useful if you need to make a hands-free phone call while in the car or when your hands are otherwise busy. If you haven’t already provided it, Google Now may ask for permission to access your device’s contacts in order to perform this action.
LPT: “Ok Google, call so and so on the speakerphone” – will call with the speakerphone on. | Reddit