Assistive technologies that continuously monitor the person with dementia’s behavioural, cognitive, and emotional state facilitate more objective means of assessing, monitoring, and supporting the individual than that provided by traditional questionnaires. The “Dementia Ambient Care” (Dem@Care) EU-FP7-funded project investigated the use of multiple wearable (actigraphy, 2D/3D cameras, microphones) and ambient (visual and infrared cameras, sleep) sensors for the recording of daily activities, lifestyle patterns, emotions, and speech, to develop a novel approach to the holistic management of dementia, in multiple care settings. This paper presents findings from the use of Dem@Care for remote monitoring and support in the home of the person with mild dementia, and for the clinical assessment and management of Behavioural and Psychological Symptoms of Dementia (BPSD) for people in more advanced stages in a residential care setting. Four ‘home’ participant cases will be discussed; two in Greece and two in Ireland. An intervention study will also be presented comprising of residents from three specialist dementia care units in northern Sweden; two in the experimental group and one in the control group. In each setting, sensor data were analysed using state-of-the-art knowledge-driven interpretation techniques based on Semantic Web technologies. Patterns of sleep, physical activity, daily living activities, and stress/anxiety over time were identified. Through specific user interfaces, clinicians and formal caregivers were able to monitor the sensor recordings and the relevant analysis in order to propose new, or to adapt older, supports and interventions. Results indicate that such sensor-based information can have a positive impact on the assessment of BPSD in residential care settings. While at home, the person with dementia and their family caregiver could monitor summaries of their own activities, and read personalized messages, prompts and advice, thus providing timely support and enabling independent living for longer.