Background Current research shows that perceived improvement of quality of life (QoL) is among the most important factors influencing acceptance of technology by older adults. Research Aim/question(s) The purpose of this study was to assess the utility of a sensor-based cognitive assistive technology (CAT) deployed in real homes and its impact on older adults’ and their informal caregivers’ perceived QoL. Methods During a period of five months, we conducted a summative evaluation by deploying a CAT in the home of couples in which one of the partners had a self-perceived memory decline. We applied a mixed method approach. Quantitative and qualitative data was collected via subjective forms, observations and 28 interviews conducted prior to the deployment, when the CAT was deployed and one month after the CAT removal. Results The study showed that the CAT had a psychosocial impact on older adults with a self-perceived memory decline and their informal caregivers but no impact on subjective forms measuring physiological and mental health, anxiety, depression or QoL. Additionally, we found that the CAT lacked a number of functionalities and that the test persons experienced several problems of different nature when using it in their homes. This affected the users’ experienced impact of the CAT. Conclusions This study contributes to the literature on sensor networks’ impact on QoL. While previous studies often use general forms intended to assess QoL, this summative evaluation indicates that using such instruments without considering contextual factors is not meaningful. The study also outlines a number of factors that sensor network providers might consider in order to increase their products impact on QoL and their perceived utility.