Monitoring indoor activities of daily living (ADLs) of a person is neither an easy nor an accurate process. It is subjected to dependency on sensor type, power supply stability, and connectivity stability without mentioning artifacts introduced by the person himself. Multiple challenges have to be overcome in this field, such as; monitoring the precise spatial location of the person, and estimating vital signs like an individuals average temperature. Privacy is another domain of the problem to be thought of with care. Identifying the persons posture without a camera is another challenge. Posture identification assists in the persons fall detection. Thermal imaging could be a proper solution for most of the mentioned challenges. It provides monitoring both the persons average temperature and spatial location while maintaining privacy. In this research, we propose an IoT system for monitoring an indoor ADL using thermal sensor array (TSA). Three classes of ADLs are introduced, which are daily activity, sleeping activity and no-activity respectively. Estimating person average temperature using TSAs is introduced as well in this paper. Results have shown that the three activity classes can be identified as well as the persons average temperature during day and night. The persons spatial location can be determined while his/her privacy is maintained as well.