There's Mycroft too: https://mycroft.ai/
We have a lot of alternatives but they are unable to get the sort of marketing and hence the attention mainstream devices like Alexa and Google Home do
That said....we are on track to have a high quality experience when we go to production in Feb 2019 ( Release 19.02 ). As an open source community we'd welcome any help folks have to offer. Contributors don't even need to know how to code, all they need to be able to do is listen to sound samples at https://home.mycroft.ai and tag them as "Hey, Mycroft" or not "Hey, Mycroft"
Thanks to everyone who is helping make Mycroft a reality!