Mobile terminal and security remote-control system and method using the mobile terminal

A security remote-control system includes a mobile terminal, a central server, and a key unit controlling the state of a lock. The mobile terminal has a positional-information detecting unit capable of detecting its own position, and automatically transmits a first email for requesting notification of the state of the lock to the central server when the mobile terminal is outside a predetermined area including a specific position specified by a user. The central server confirms the state of the lock through the key unit, when the central server receives the first email, and transmits to the mobile terminal a state notification email indicating the state of the lock. The mobile terminal automatically transmits to the central server a second email for instructing shutting of the lock when determining that the lock is not shut. The central server transmits to the key unit a locking instruction signal.