This paper presents the design, implementation and early tests of an app that collects a comprehensive set of health-related data, as part of the EU-project WARIFA. To achieve the main aim of the project – using AI to prevent chronic conditions – a wide range of data needs to be collected and stored at a backend server for processing. The methods and elements for creating this system are presented, as well as results from the co-creation process and early user-tests. Challenges regarding complexity, security, and privacy are discussed, as well as the needs and prospectives for easier ways of collecting health-related data.