Maybe a smart thermostat or something.Do not let tenants dictate your upgrades - they sound like a PIA, honestly.

Unless you get the utilities separated along with separate heating for each unit, you'll never find a 'fair*' way to distribute costs IF the tenants themselves have access to the thermostat, a/c, hot water etc.

I'd install a programmable thermostat - assuming it's a central air unit.  

The thermostat is on the 2nd floor and is set to 72.

Maybe some startup types that are ok if their programmers don't have windows?

Then you meet them at the property, hand them the key and give expectations such as when and how to replace air filters, properly use the thermostat including making sure the fan is on 'auto' and never 'on', where the trash/recycling cans are kept and when to put them at the curb, etc. 

We replaced the thermostats with thermostats that max out at 72 degrees.  

I haven't yet targeted specific commuting professionals, but heard a podcast where the investor advertised offering tech packages to attract young professionals: usb outlets, smart doorbell, lighting and thermostat.

It should be in your property management agreement - all the fees your PM charging.They all go in your tax return as expenses and decrease your profit.When you signed the PM agreement, you should have to negotiate everything which looks unusual for you.If you pay money for placing Tenant, showings are included in that.Software is a Programm for PM?

Just watch "Jobs", the movie about Steve Jobs, where hundreds of people said NO to his product, and even his programmer said "But Steve, nobody, NOBODY would ever buy a computer!!!!!!!"