The “challenge” I see with using any Android or iOS device that is “mounted” anywhere is what are you planning to do in 3 years when they either fail or cannot no longer be upgraded to a relevant OS that is required to run the apps?
I had friends who went down this path with their A/V systems in the late 2000’s and early 2010’s. Bought a couple of iPADs along with fancy in-wall mounts that controlled large portions of their houses. It was pretty darn impressive. Now 4+ years later, they have this old iPAD mounted in the wall that is useless because the required iOS version to run the automation apps isn’t supported on the hardware. They can’t just buy a new iPAD since the mounting plate/dock doesn’t work for it.
Just my fears.
Also very curious on the plans for mounting and charging the devices? I do have an older phone that lays around my living room and kitchen for guests to be able to control lights and the Sonos, but it ends up dead all the time since nobody else but me makes the effort to go plug it back in every couple of days.