Lifestyle, disease and biology put older people at risk of functional decline, leading to falls, cognitive impairment, frailty, and negative consequences for quality of life. PreventIT develops and tests an ICT-based mHealth system for the consumer market that 1) enables early identification of risk of age-related functional decline, and 2) engenders behavioural change in younger older adults in order to adopt a healthy, active lifestyle. We use an integrated system of a smartphone/watch as frontend technology and a protected cloud-based solution for handling of personal data as backend technology. We are developing online instruments for risk-screening, complexity metrics, motivation for behavioural change, and a method for personalising exercises by phenotype, based on currently available big data sets. The ICT-based intervention we develop is unique, delivered on a smartphone/watch with exercises integrated in daily life, and firmly grounded in a behaviour change programme. We will evaluate the role of technology and behavioural change theories in risk prevention by performing a multinational feasibility RCT to compare our ICT-based intervention with 1) the same intervention without use of technology, and 2) practice as usual. Usability and feasibility are in focus, and ageing people are included in all phases of the project. At the end of the project, all assessment and intervention components will be integrated into a personalised self-administered activity system, designed to empower ageing people to take control of their own health and function. A microsimulation health economics model will be developed to predict effects of our risk prevention intervention on carers and the health care system. PreventIT is performed by a strong interdisciplinary team with previous impact in the field of ageing and ICT, and commercial partners who are strong on technology development and exploitation are included to increase the chances for iPAS to become a first choice mHealth system for the ageing generation.