@Loren Thomashere is an interesting scenario.We found a 240v feed to a wall heater with blower, (fed through a double pole thermostat), that also feeds a 240v window a/c that is wired behind the heater inside the wall.

Finally, I want a remote thermostat, security cameras, maybe light controls too --- so I'm thinking of a SmartThings, Wink2, or Nexia home automation option with a Schlage or Kwikset z-wave compatible lock.

You go and figure out the batteries in the thermostat are dead.  

It does not have a thermostat that can be adjusted regularly like modern day tech.

(igniter, thermostat, ?). 

The Honeywell system with wireless thermostats seemed like a good solution. 

Other than that, simply write him a letter stating the heat works, and for the apartment to be warm, it needs to be controlled by the thermostat and that there isn't anything to "FIX", and to stop contacting you except to pay rent or report emergencies.Do not renew his lease.This being said, do check your windows. 

But there would only be one thermostat for the property.

For thermostat batteries, and other batteries I ask them to do it but I change them where needed. 

Was wondering what's the best brand for thermostats / can be locked at a temperature to install in my properties?