Sure, that would work if you just have your useless box switch app subscribe to the binary switch going off and turn it back on. And don’t have turning it on do anything at all. That way it would be ready for the next “off” command.
But then you have to always have the binary switch turn your devices off. If somebody grabs the button remote and turns the TV off you might be out of sync. Because you never touched your binary switch that way.
( harmony used to have a power off activity associated with the off button, but they don’t anymore. Now physically pressing the off button on one of their remotes turns off whatever entertainment activity is currently active.)
What most of us do instead is to add turning the virtual binary switch on as a start step to every harmony activity. That way no matter what you do to turn things on, the binary switch is sitting ready to turn the master device off again.
For example, I have voice controls for:
“Turn Netflix on”
Turn ESPN TV on"
“Turn DVD on”
“Turn Roku on”
Or my housemate might turn the TV on from the harmony button remote or from the harmony app. It doesn’t matter, because harmony is based on activities, and we have turn the virtual binary switch (called “theatre” ) on in every activity.
Harmony will not turn off a device which is needed in the next activity. So it just stays on the whole time.
Then when I use the voice command “turn theater off” that triggers an activity which turns off the master power device, in my case, the TV.
I can call the virtual binary switch whatever I want to in echo using groups, so if I wanted to call a TV I could. As long as I didn’t have another switch also called TV.
In my scenario, I turn on content and I turn off devices. So it’s easy to remember and feels natural for us even though we don’t have one switch that is both turned on and off by voice. We never try to “turn on theater.” That’s only used for off.
It is possible to get an out of sync condition this way where my housemate uses the button remote to turn the TV off, the virtual binary switch for theater might be left on. But I don’t care. It’s just like your useless box app. Being on is unimportant except that it needs to be on right before I want to turn it off by voice. I don’t check the status on that or anything.
If I did want to check the status on that it gets trickier, and that’s where your useless box smart app would fill that gap. But then you have the synchronization problem of someone using the physical remote button.
So just comes down to exactly how you are going to use it and which gaps you need to fill.
At my house, I use voice for the TV and my housemate uses the physical remote. So keeping those in synch is the biggest issue for us. If you never use the physical remote and you want to reduce the effort it takes to set up new activities, then the useless box approach would be better.