Abstract: A building monitoring system that provides detection of anomalous conditions in the building, including water leaks, or the like. The system includes a central unit operatively connected to a plurality of sensor devices which are used to detect the anomalous condition. The central unit alerts the user of the anomalous condition, and take action to minimize the damage from the condition, such as activating a water shutoff valve or the like. The system also preferably includes a system for actively monitoring the status of the sensors to determine that the sensor, and the overall monitoring system is working properly.