You will need
Set up on your phone the delivery report of SMS messages. To do this, go to the relevant menu and set the desired report parameters. If you are interested in the phone of the subscriber is enabled, after some time, you will receive a message about the delivery. It usually takes about a minute with a good signal provider.
If you want to know whether the subscriber's phone at the moment, in the settings of SMS messages in your phone, set a minimum waiting period of delivery. Send the caller a text message. In cases when the phone is turned off, the screen displays information about failed to send or that it was sent, but is pending the activity of the SIM card of the subscriber. Time may be limited depending on the servicing you, operator.
In order to know when the number of a subscriber is available, put in the settings SMS or other maximum required waiting period for delivery. Send a message to the desired number and wait to receive a delivery report.
To check if phone a particular phone number, dial his phone number. If you don't want to let them know your phone number, hide it by connecting the service caller identity restriction, calling your service provider or just by using a different number.
If you want to find out if lost your phone, contact local police statement, attaching documents confirming ownership of the device on which the mandatory ID. Data will be transferred by the operator, and, when enabled, your phone ID will be sent to a special number, and then his location will be discovered, and the mobile device will be returned to you.
Do not use special programs to determine the status of the phone.