Hi guys. I need some help directing me to make an informed purchase decision on devices.

Before I commit to buying the devices for the home I wanted to make sure I can actually run the scenarios I want using the Apple Home app or possibly another app that works in conjunction with it.

I want to have occupancy sensor detect if room is occupied, then read the temperature in the room using a temperature sensor, then trigger the fan to run if the temperature is above what is set for the room, adjusting the speed from 25% to 75% and back down depending on how close to the target temperature the room reaches (basically mimic the behavior of a smart HVAC thermostat but kicking on a ceiling fan instead) However if the room is unoccupied then no need to run the fan at all and if the room becomes unoccupied then turn the fan off.

Is this possible through scenes and automations?

If not directly through the Home app then perhaps through a 3rd party app that I don’t ever want to open again on my phone except to change settings or do initial setup?

If the app has to be running all the time like a server then an app that can live on my Mac running in the background but have an iOS app as well to sync settings and whatnot (like iCloud based or something).

I have an always on 24/7 Mac at home fwiw and I don’t mind having an app running in the background on it to execute such commands as long as it can survive restarts and power failures.

Thanks for any input!