Prevention of disease and disability starts with a healthy lifestyle, and the one factor typically heralded for both its preventive and rehabilitative power is physical activity. But despite extensive knowledge about the importance of an active lifestyle for our overall health and function, two-thirds of the population is less active than recommended and particularly retirement is a period in which activity levels drop further. Technology can be used to activate and motivate people, and is especially powerful when tailored to an individual’s needs, challenges, and barriers. In addition, technology can help people to take responsibility for their own health and function from a very early stage onwards, before gradual age-related decline in underlying functions manifest themselves as growing difficulties performing activities in daily life.