An accelerometer is a device that measures physical acceleration, or the rate at which something is changing its velocity. Accelerometers are most commonly used to measure the acceleration of vehicles, including cars and planes, as well as in electronic devices such as smartphones. They can also be used to measure the force of gravity, in which case they are referred to as gravity probes. Some accelerometers even contain thermometers and other sensors to measure other physical phenomena. Accelerometers are commonly used in the automotive, aerospace and sports industries for motion sensing and navigation.