Wearable technologies increase the ability to track different parameters related to health and well-being. As the variety and amount of data sources grow, a better understanding of health-related data can be obtained through research on data fusion. Outcomes can either be validated by end users when results are finalized or throughout the design and development process of mobile health applications. This chapter addresses the co-creation methodology applied for the creation of a mobile health application, called Vire, and the backend, called Synergy, to serve personal data to the mobile health application. Synergy provides an interface for the research team to interact with participants and visualizes parameters relevant to the study. Modern frameworks and platforms, such as React Native and Meteor, are used to facilitate the adaptiveness and functionality required for the co-creation of Vire. The chapter concludes by addressing the findings from the study with 26 participants.