A facility monitoring system and application receives and interprets readings from multiple sensors for determining a condition, alert or alarm and initiating appropriate notifications. Low-cost, deployed sensors detect or receive a parameter pertaining to a condition in a physical space, such as temperature, electric flow, or an open door. A channel to a remote monitoring server or application receives and reports the reading via a user accessible GUI (graphical user interface). A compound or aggregate value is computed from multiple channels based on readings from a plurality of sensors, thus allowing reporting of conclusory conditions based on several related readings, rather than a single scalar sensor value that imposes a burden on the user to deduce or investigate other related sensor readings. A GUI receives aggregation processor defining computations to be performed on readings from the multiple sensors, and alert processor defining conditions and alerts representative of issues requiring attention.