My paraplegic friend hasn't had any success with voice recognition software.  But, he has Alexa and it understands him.  I found that Alexa can control a computer, but it seems to do it with Echo.  
I'm confused by what I'm reading with regard to using Alexa.  Does it need Echo, is that a separate device, do you need Alexa or just Echo?

Has anybody worked with this system?

I would really like to get him something working.  

Please don't suggest Dragon Naturally Speaking, he had it and couldn't make it work.  

I think the best option is using Alexa with the special software from Alexa.