https://www.theverge.com/2019/1/10/18176272/amazon-alexa-assistant-devices-ces-2019-tvs-soundbars-smart-speakers-kitchen-bathroom-cars

Voice assistants are being integrated into every part of our daily lives, from smart speakers to home security and bizarrely, even to toilets. Google said it expects its Assistant to be installed on a billion devices soon, and Amazon recently announced that more than 100 million devices with Alexa have been sold.

So Amazon’s number isn’t a billion (it isn’t on millions of Android phones, after all), but support for Alexa continues to be built into more and more products, thanks in part to the Alexa Gadgets Toolkit launch last year, which gives developers APIs and technical documentation to make gadgets that can pair up with an Alexa device.