We have a Crestron Pyng as the central hub with attached goodies.
We also have our own Raspberry Pi based data logger that captures up to 40+ channels of temperature, humidity, luminance, occupancy, and thinking about a thermal imaging camera. Also can capture circuit based power usage and PV production to get a better sense of consumption/production cycles.
Keyless locks Dropcam Operable shading Lutron Pico wireless light switching with scenes Leak Detection Remote management/security (AirBnB) features. Whole home media etc.
We are looking at appliance connectivity, but want real function not just gadgetry. It's an quickly changing landscape, so the list will grow and morph, but pushing for real utility and performance enhancing tech.
Bringing this all under one central control hub would probably take an equal stakeholder in your business. It's just as important as the material aspect of the home. If you don't have the wherewithal for this, you should probably avoid doing ANY kind of fancy electronic stuff. I know the PV panels are a non-negotiable... but I would suggest not going beyond that until you can create an SDK. This manages expectations, and paves a sane "upgrade" path for the hardware. Simple is always better than fancy.