Nap Alarm is an innovative, potentially lifesaving anti-drowsiness alarm. It is worn over the ear and has an electronic position sensor. When your head nods forward, it sounds a loud alarm to instantly wake you and alert your passengers. The Nap Alarm is not only designed for drivers, it is also perfect for people who need to be fully alert while on duty, for example, security guards, machine operators and even students while studying or where concentration is required. Makes a perfect gift. Uses three AG3 alkaline button cell batteries (included).