Abstract: A thermostat according to the present invention is capable of capturing audio commands from a user for controlling HVAC systems. The thermostat can operate in training mode and control mode. In training mode, the user can tailor a list of predefined keywords with his voice and, in control mode, the user can change HVAC system settings. Optionally, the thermostat is equipped to interface with a remote unit. The user can speak audio commands into the remote unit, and the remote unit will transmit his commands to the thermostat.