With the recent discussions about voice security and the release of iOS 10 and the homekit home app, I just thought I’d mention our setup in case it’s of interest to anyone else. Because I’m quadriparetic, I rely very heavily on handsfree voice control.
We do have a number of HomeKit devices, but only those which are also controllable with echo.
Siri is smarter, but Echo hears better
There’s no question Siri is smarter than echo. You can ask a status question, like are the downstairs lights on? And get an answer from Siri. Siri also knows that a light is a light and understands rooms, so you can say “turn on the kitchen lights” and any light that is in that room comes on. You don’t have to have created group names or anything like that. So there’s a lot less set up work with HomeKit. You scan the device barcode, assign it to your room, and give it a name. And that’s it. With echo you have to authorize, Discover, and group. None of the steps are difficult, but it’s easy to forget one and then wonder why the light didn’t come on with the others. ( I know you can get status responses from the askAlexa smartapp developed for SmartThings, but that’s a lot more set up then I wanted to do. )
But as far as practical voice recognition goes, echo wins by a mile. Once we’ve completed voice training, I hardly ever have to repeat myself with echo. Siri still misses about 20% of the time.
sometimes Siri is too smart
Siri understands “unlock all doors.” So security is toast if anyone is within listening range of an always listening device on your HomeKit network. They don’t have to know what you named anything. 
At the same time, I don’t like to have echo associated with the lock because I do get more random activations with echo, in particular in response to things said on television.
enter the watch…
Siri on the watch is pretty secure, though. It can be voice trained to an individual voice, which isn’t perfect but does add some security. The watch is always locked and not always listening but is very simple to activate with a single arm movement. At that range, recognition accuracy is much better.
The end result is that I can choose to unlock the front door by voice without getting up (I also have a video doorbell to know who’s there) but nobody shouting in the front yard could unlock the doors and random television comments won’t do it either.
If you have a watch that can do voice texts, you can send a text to IFTTT which will then trigger a SmartThings command to unlock a Z wave lock, so you can do the same thing even with a different set of devices.
A little of this, a little of that
So we use echo for all voice control of lights in the house because it just works much better.
We use a smart watch voice option when we want to manage locks.
We do not have Siri on always listening on other devices.
Other setups will work for other households, but I just thought I’d mention that this is what’s working for us. 
