The patented “Thermostat Lite” fits on a standard round thermostat to eliminate the need to light up an entire room to read the thermostat displays, says the company. It has a glow-in-the-dark button for access. With one touch, the entire thermostat lights up. No wiring or screws are needed for installation. It replaces the regular thermostat cover with a snap, the manufacturer says. Two AA alkaline batteries and a lifetime guarantee are provided with each unit.