I was planning to buy an Amazon Dot personal assistant before Christmas, but a Black Friday discount pushed me into ordering it a little earlier. Unfortunately it hasn't arrived yet. I'll be sure to report on what I think of it. I hope to have it controlling some other devices on my network including my lights via Home Assistant.
Meanwhile, I heard about the Adrian Project that aims to give similar functionality using a Raspberry Pi and some open source software. I think they must be using Google's voice recognition API as the Pi is not really powerful to do it alone, but I may be wrong.
A similar project is Mycroft that also uses a Pi. They seem to be having issues in delivering the hardware that some people pre-ordered. It certainly looks cute.
The Dot is cheap enough to try out for now and I'll see how the open source solutions develop.
Of course it could all go horribly wrong...