In this study, we proposed a non-intrusive occupancy monitoring approach which leverages on existing BLE technologies found in smartphone devices to track the occupants' movement patterns using BLE beacons. Unlike existing methods, the proposed approach does not require the installation of a mobile application and only requires the occupants to provide the MAC address of their Bluetooth-enabled smartphone devices. The feasibility of the proposed approach was demonstrated by conducting a two-week data collection effort in a university office environment where the occupancy patterns identified are used to develop various occupancy profiles for different types of occupants.