A magnetometer is a tool or instrument that measures the magnetization of an item or the force of a magnet. The magnetometer typically looks at the Earth's magnetic field and local magnetic field in order to determine the location and vector of a magnetic force.
Techopedia explains Magnetometer
Magnetometers are used extensively in different kinds of industries, including high-tech ones. One prime use of the magnetometer is in the security industry, where it is used to detect certain kinds of metals used in firearms.
Although some uses of magnetometers are currently in place in industries, others are largely theoretical. For example, the use of magnetic levitation or "maglev" trains is currently part of the transportation industry; however, individuals such as Tesla pioneer Elon Musk are now talking about theoretical high-speed tube transportation that would also use magnetic force as an energy source.