This paper reports the description of a multi-sensor platform able to automatically assess the level of physical activity and sedentary time of older adults. The platform has a hierarchical network topology, compound by N detector nodes managing several ambient sensor nodes and one detector node that manages a wearable sensor node. The system provides also one coordinator node that receives high-level reports from detector nodes. The idea of using heterogeneous sensors is motivated by the fact that in this way we expands the number of end-users, as they may accept only a type of sensor technology. The objective assessment was conducted through two main algorithmic steps: (1) recognition of well-defined set of human activities, detected by a 3D vision sensor (ambient node) and a smart garment (wearable sensor node), and (2) estimation of a physiological measure, that is (MET)-minutes. Results …