Fortunately everything is "smart" these days; thermostats, appliances, and even door locks.  

We also have a Emerson Sensi thermostat that is WiFi.

I have wifi thermostats.

If you would like, I can search for possible remedies or components that can be replaced within the fridge (circuit board, thermostat, etc), though the unit is 17 years old and I'm not sure what parts may still be available."

Beats rewiring :)Wireless Light Switch and Receiver Kit, Wall Switch Remote Control Lighting Fixture for Ceiling Lights, Fans, Lamps, No in-Wall Wiring Required, 100 Ft RF Range, Programmable

The full service option typically charges 15-25% of rental income, possibly a monthly fee and provides all services needed, bookings, guest check ins, guest complaints, maintenance, housekeeping, inspections and maybe even payment of STR taxes after guests leave.I am more hands on in my rental and have smart devices that make my life a little easier, smart locks, smart exterior lighting, smart thermostat, loud noise indicators and smart smoke detector. 

Our thermostat (Emerson Sensi) sends me details like humidity etc based on preset alerts.

Millions of people and many 10,000s of programmers have tried to monetize the space.

Each floor has separate thermostat there are both on separate breakers one unit is a 3 bedroom the 2nd unit said 2 bedroom

Also control the thermostat yourself.