One of the latest developments in this area are programs created to track a cell phone location online  https://www.hoverwatch.com/track-phone-location . It is virtually impossible to imagine a modern person without a mobile phone, even the smallest children have them, so with the advent of the appropriate software, it has become quite simple to control their place of stay. In addition, such programs are necessary if a person is in trouble, lost or something happened to him - help services (police, ambulance) will be able to quickly find a subscriber.