It’s an Under Floor Heating Thermostat - also Z-Wave and connected to Smartthings. (see here)
The reason they can be placed together is that both the wall controller and the thermostat conform to the standard EU 55 faceplates and mounts - there are quite a lot of other products out there that fit as well so worth looking into - its a bit of a minefield trying to find all the right bits but well worth it in the end