If you want to know about the movements of your child or elderly relative that does not always answer the phone, and you prefer to know where one of them can wait or look for, then if the phone issued in your name, ask the operator, not do they provide services to locate the phone. Every phone is constantly searching for network, bearing cell towers, and the operator with a precision of ten meters may calculate the location of the subscriber. This service can be paid for each definition, or cost a certain amount times per month.
Most modern phones are equipped with GPS-receivers, which are much easier to find my phone. There are programs that are installed on the phone and computer simultaneously. If you make a request from the computer, the phone immediately respond and give you your coordinates. But even if the phone does not have built-in GPS, it will still be able to navigate in space using the same cell tower. Special attention should be paid to so-called an alarm tracking programs that you can install to your phone, and from time to time to forget. If the phone suddenly will be stolen or lost, the program will prompt the new owner to enter a password and if correct password is not specified, the program will send SMS with coordinates of the phone in the room. This program will work and send SMS about location, even if the new owner inserts a new SIM card. Thus, you can easily find your phone and return it.