Phonelocator periodic is a free service to help you keep tabs on the location of your phone. It runs in the background and can periodically update the phone's location to the Phonelocator server. Updates can also be triggered remotely by sending a text message to the phone that starts with the word 'Update'. You can also nominate a friend to receive a 'buddy message' when the SIM card in your phone is changed. If your phone is stolen and the SIM card is changed, your buddy should receive a text messaged containing the thief's telephone number.
Phonelocator periodic is not intended to be a real time tracker! It's designed to be run all the time and periodically update the phone's location without a noticeable effect on the phone's battery life.