You make a good point re: Nest. I am kind of a doomer on home automation market in that I have been an early adopter and it's been around 15 years, but most people just don't care about the space.
The home automation stuff people are interested in and Apple could attack is the doorbell/camera/alarm systems because what is out there is still genuinely a minefield of awful products. An Apple it-just-works premium offering would sell. And they have the physical store footprint to demo them.