A security system according to an embodiment of the invention includes motion sensor units for positioning at desired locations of a building structure. Each motion sensor unit includes a motion sensor adapted for detecting motion external to the building structure. The system can include a mobile alarm display unit operatively connected to the motion sensor units. The mobile alarm display unit can include a plurality of alarm indicators corresponding to the motion sensor units. Each alarm indicator can be operatively linked to a particular one of the motion sensor units, and detection of motion by the particular motion sensor unit activates the corresponding alarm indicator linked to the particular motion sensor unit.