A very basic question. How do you subscribe to hello home actions in a SmartApp? Not to be confused with mode change.
Suppose I have hello home phrases like:
“Lights on at Sunset”
“Turn on Family Room Lights”
Is there a way to capture when these events happens in your code?
Create a virtual switch that corresponds to a phrase. When phrase is executed, have it trigger a switch and subscribe to switch events as usual.
It’s a hack, but so is everything else.
Hats off to you, Alex! 
So basically there is no “proper” way to subscribe to a hello home phrase actions.
Not only is there no “proper” way, there is no way at all. Because, Hello Home phrases are just apps. The Tile Buttons, momentary and on/off, are built-in device types to accomplish this. The phrase turns them on or off, your app has subscribed to those events, the rest is up to your imagination…
Darn. 
20.5 characters
Can you tell us your use case??
Some of these SmartThings “quirks” (or “inflexibilities”) are, pardon the cliché, actually features.
More precisely, some of our peeves are intentional in the design of the platform.
The problem is that there is insufficient guideline documentation to help us understand what is a bug vs feature vs. workaround vs. proper usage…r