Google built a little rollercoaster for CES this year to showcase its voice assistant technology, and how it works both in and out of the home. While the ride is cute and buzzy, Google's vocal voice push should be making Amazon nervous, says Jared Belsky, CEO of 360i, an agency that literally wrote the voice playbook for marketers.

Although we are now just a couple of years into the development of voice and smart speaker technology, a duopoly has already emerged, says Belsky. An entire cottage industry of third-party products has blossomed around the two — smart light switches and smart microwaves that boast "works with Alexa" or Google. It has created, says Belsky, a "flywheel" effect that serves only to strengthen the duopoly's dominance.

However, if Belsky were to place a bet, he'd say that Google has the advantage. He points to research from Forrester that suggests 72 percent of assistant interaction is done on mobile devices.

"The war on voice is going to be won in your pocket, on your mobile device. Not your smart speaker," he says. "What's less understood is that Google is coming on extraordinarily strong, and their advantage is the smartphone. It's Android; it's what's in your pocket. That's going to lead to a lot of strength for Google."

Still, Belsky isn't ready to call it game over just yet.

He also has some advice for marketers when approaching this burgeoning landscape: Know your goals.

"if you're a CMO, the first thing is you have to ask yourself is what's your strategy — is it entertainment- based strategy or is it utility-based?" he asks.

A rental car company, for example, would probably do well to have a voice strategy built on utility, with FAQs, instructions and rental services. A cable company, on the other hand, might want an entertainment-centric approach that highlights its original programming.