A heating, ventilation, or air conditioning (HVAC) system includes a headless thermostat device and an adapter unit. The headless thermostat device includes one or more circuits configured to receive a control input from a user device via a local wireless network and generate a control signal for HVAC equipment based on the control input. The adapter unit includes one or more circuit configured to receive the control signal from the headless thermostat device via the local wireless network and provide the control signal to the HVAC equipment for operation of the HVAC equipment in accordance with the control input.