- Having smart locks means I don't have to give out keys, and I can change lock codes remotely.
- Having a smart thermostat means not only can I change it remotely (once they've checked or to prepare it before checking in), but I also get notified of when the HVAC isn't working. (For example, the ecobee will email you if it's been heating for a couple of hours and the temperature has dropped). This is absolutely necessary in climates with periods of extreme cold as that can cause burst pipes, which then damage everything.
- Smart smoke detectors, CO2 detectors can notify you of problems that you won't otherwise find out about in a timely manner, given you're not at the location.
- Sensors that detect flooding. We have a condo that has been flooded by upstairs tenants. Putting a moisture detector between the walls means we get notified of a small problem before it becomes a huge problem.
I think having a smart home is even more important for a property that you don't live at then one where you do.
Actively telling guests "We don't have hidden cameras" has got to be extremely off-putting. There is not a huge problem with hidden cameras. Just fine/arrest/ban the hosts who actually do it, given evidence that it is them doing it.