These are standalone/portable thermostats, i.e. they don’t physically connect to any wires or heating devices. So if you’re using external relays to control your heating (furnace, heaters, radiators etc) you can use this thermostat along with the SmartThings Automation tool to control your heating (like explained in the first post). So the thermostat can be next to your bedside while the switches/relays can be anywhere across the home or on any floor.
These are different from traditional thermostats and SmartApps used to program traditional thermostats because traditional thermostats physically connect to HVAC’s or heating/cooling devices using wires and control them directly. This thermostat doesn’t, so you’ll need to use the SmartThings automation tool or SmartApps which support controlling relays/switches to control temperature (like this listed in the first post).
The proximity sensor is used to turn on/off the thermostat display LED’s to conserve the battery, it only activates when you’re within a few inches of the device so it can’t serve as a while room proximity sensor. However some of the SmartApps in the first post like the Motion Sensor Thermostat with Remote temperature sensors, Presence detection and Schedules support using regular/standalone motion sensors as proximity sensors to trigger the thermostat heating/cooling only when someone is in the room.