I have an interesting challenge: I want to add IoT tools in several apartments and allow my guests to control them through an app. Currently I already have an

I have an interesting challenge: I want to add IoT tools in several apartments and allow my guests to control them through an app. Currently I already have an app, but no IoT integrations (basically just reservation). How to do it safely? Also, which automations would be nice to have but not so obvious? Thinking from things like light control, but also checking the apartment energy consumption in order to detect appliances that need maintenance before they break.