A free-fall sensor is a component of electronic devices that detects them being in a state of free fall (after being dropped).

Use

It is usually used to then apply safety measures, e.g. parking the head of a hard disk

Hard disk

A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...

 to prevent a head crash

Head crash

A head crash is a hard-disk failure that occurs when a read–write head of a hard disk drive comes in contact with its rotating platter, resulting in permanent and usually irreparable damage to the magnetic media on the platter surface....

 and resulting data loss upon impact. This device is included in the many common computer and consumer electronic products that are produced by a variety of manufacturers.

It is also used in some data logger

Data logger

A data logger is an electronic device that records data over time or in relation to location either with a built in instrument or sensor or via external instruments and sensors. Increasingly, but not entirely, they are based on a digital processor...

s to monitor handling operations for shipping container

Shipping container

A shipping container is a container with strength suitable to withstand shipment, storage, and handling. Shipping containers range from large reusable steel boxes used for intermodal shipments to the ubiquitous corrugated boxes...

s. The length of time in free fall is used to calculate the height of drop and to estimate the shock to the package.