I haven't bothered getting the SDK for the Kinect 2 yet but both of them seem to only be good for about 135 degrees around the device - the Echo is a much better omnidirectional microphone.

The kinect seems pretty cool. I've heard of one person who brought it into work and used it to identify and greet people who walked into his office. So there is probably some pretty cool user identification projects you could do with it.

My (admittedly anecdotal) experience having an Xbox One is that it would pick up phrases that barely sounded like built in triggers and do unexpected things at unexpected times, such that I felt forced to disable it.

We've had an Echo since before they were available to the public (ex-Amazon employee here), and it does occasionally beep when it thinks it hears "Alexa."

But it's very rare that it goes beyond that; usually we hear the beep and one of us will yell "never mind!", and then the Echo will go silent. Sometimes it will cancel itself, too. I think that the always-listening part is less discriminating than the active voice recognition, and that it can re-parse the last couple of seconds and decide, in retrospect, that you didn't say "Alexa."

That said, I just recently said to my wife, "I wonder if Alexa knows 'sudo make me a sandwich'". The timing was such that it parsed "sudo make me a sandwich" and answered, "Well, if you ask like that, how can I refuse?" :)

We had a good laugh. Funny thing was, looking at the app later, it was actually parsed as "Pseudo make me a sandwich." I bet Google Now would have corrected it to sudo. :)