A system and method used for monitoring conditions in a space through characterizing detected occupants with properties in accordance with time, location and tracked traversal path. The intruder as a detected occupant is distinguished from the tenant, property management staff, and visitor. The system triggers an alert indicative of a condition by sending signals and messages to selected devices or systems as receiving nodes. A condition, such as collected sensor data incompliant to a threshold, is detected and an alert is triggered. A user carried mobile device such as the cellular phone, elevator control system operative in a building are possible receiving nodes of a triggered alert for a detected condition.