Landlord Thermostat Recommendations?

[William Conrad]

I'm looking for a good landlord thermostat. In the multi-family I own, two furnaces heat four apartments, so there is no way for me to divide the heating bill amongst the tenants. So, my best bet is to make the apartments as efficient as possible and control the heating from remotely. I'm looking for something that gives me remote access and isn't hackable by the tenants. If they aren't paying for the heat, they have no incentive be smart about the heating bill. So, it falls on me to monitor it. Any good thermostat products out there I should know about?  Thanks for the help!