Depends on what device it is to what apps that provide tracking capabilities however: -
It is illegal in the UK to use spyware on a spouse without their permission. The Crown Prosecution Service says there aren't specific laws related to the use of stalkerware but any criminal activity like this can be prosecuted by a number of means including the Protection from Harassment Act 1997.
If it for your children who’s under the age of 18 and you are their parent or legal guardian, you have a complete legal right to use a GPS tracking device to track their location.
Eddy
