Smart Thermostat Recommendations

[Brad Eckert]

I have a four plex that runs on oil that heats the entire building. The thermostat is in a common area and the tenants continuously crank it up to absurdly hot temperatures. I would like to purchase a smart thermostat that I can control from my phone and will have a locked screen to prevent tampering. I'm about 90 miles away, not sure if distance will play a factor. Does anyone have any recommendations for a thermostat? Thank you!