The security device contains at least a main unit with a number of wired external sensors and detectors. The main unit itself has built-in image capturing and motion detection capabilities that can be operated independently or to provide additional confirmation to the events detected by the external sensors and detectors. The main unit contains a radio transceiver member capable of conducting two-way, real-time and message-based, mobile communications via a mobile communication network. As such, whenever some abnormality is detected, the main unit is able to dial a specific party to play pre-recorded voice message and/or send captured images or video clips in real time or in some messages.