A GPS tracking unit is a device, normally carried by a moving vehicle or person, that uses the Global Positioning System to determine and track its precise location, and hence that of its carrier, at intervals. The recorded location data can be stored within the tracking unit, or it may be transmitted to a central location data base, or Internet-connected computer, using a cellular (GPRS or SMS), or satellite modem embedded in the unit. This allows the asset's location to be displayed against a map backdrop either in real time or when analyzing the track later, using GPS tracking software. Data tracking software is available for smart phones with GPS capability.

Personal tracking

Law enforcement. An arrested suspect out on bail may have to wear a GPS tracker, usually an ankle monitor, as a bail condition. GPS tracking may also be ordered for persons subject to a restraining order.

Race control. In some sports, such as gliding, participants are required to carry a tracker. In particular this allows race officials to know if the participants are cheating, taking unexpected shortcuts, and how far apart they are. This use was illustrated in the movie Rat Race.

Espionage/surveillance. A tracker on a person or vehicle allows movements to be tracked. This application is used by private investigators.

These devices are also used by some parents to track their children. Some devices can send text alerts to the parents for every unexpected place visited by the child.

GPS personal tracking devices are used in the care of the elderly and vulnerable. Devices allow users to call for assistance and optionally allow designated carers to locate the user's position, typically within 5 to 10 meters. Their use helps promote independent living and social inclusion for the elderly. Devices often incorporate either 1-way or 2-way voice communication. Some devices also allow the user to call several phone numbers using pr-programmed speed dial buttons. Trials using GPS personal tracking devices are also underway in several countries for use with early stage dementia.

Some Internet Web 2.0 pioneers have created their own personal web pages that show their position constantly, and in real time, on a map within their website. These usually use data push from a GPS enabled cell phone or a personal GPS tracker.

Sports: the movements of a rambler, cyclist, etc., can be tracked. Statistics such as instantaneous and average speed, and distance traveled, are logged.

Adventure sports: GPS tracking devices such as the SPOT Satellite Messenger are available that allow the position of a person to be tracked. In particular this allows rescue personnel to locate the carrier. These devices allow the carrier to send messages, even when out of cellular telephone range[citation needed].

Monitoring employees. GPS-handled tracking devices with built-in cellphone are used to monitor employees by various companies, specially those engaged in field work.

Asset tracking

Solar Powered. The advantage of some solar powered units is that they have much more power over their lifetime than battery powered units. This gives them the advantage to report their position and status much more often than battery units which need to conserve their energy to extend their life. Some wireless solar powered units can report more than 20,000 times per year and work indefinitely on solar power eliminating the need to change batteries.

Animal control. When put on a wildlife animal (e.g. in a collar), it allows scientists to study its activities and migration patterns. Vaginal implant transmitters mark the location where pregnant females give birth. Animal tracking collars may also be put on domestic animals, to locate them in case they get lost.