Andrew Essex — the CEO of Plan A and author of "The End of Advertising" — has a word of advice for marketers when it comes to their voice strategy: Take a cue from podcasts.

"The people who are working in voice can learn a lot from podcasting," he says. Marketers should see it as a "privilege to talk to people in their ears."

From the floor of CES extention at the Aria Hotel at Las Vegas this week, Essex cautioned marketers to remember context above all else.

"You have to respect their situation and not interfere, not intrude," he says. "The device can listen and it can talk. When a consumer wants to hear something, they don't want an ad, they want utility. If you want tell them something, be brief and be functional."

And despite voice providing marketers with new avenues to reach people, he says they should wary.

"Brands should mostly be scared of voice because voice has a tendency to get rid of brands. People want toothpaste and toilet paper. They don't necessarily want Crest," he says. "Be careful, because sometimes brand can become inessential in the world of voice."