Amazon lost the phone and tablet wars, so they shifted their focus to the voice assistant market, and are now ahead of competitors with their Alexa skills SDK. It's great to see Google now step up too. I expect Microsoft and Apple follow suit.

It's pretty easy to imagine how one could port simple 'voice command' apps between platforms ('hey, order a pizza/uber/etc...). Over time, however, these platforms should emerge into substantial AI. To be useful they will need to remember and understand more subtle contexts. "Hey, what's the score of the game" will have to remember that I like the Seahawks and Sounders, but only the Sounders are playing live right now, etc...

I like Google's choice to include a "conversational" model to the application design. "Let me talk to <x>" is pretty natural and allows <x> to then have full control of the interaction. Alexa's "ask <x> to <command>" model makes it easier to fire off simple commands, but awkward for deeper ones.