The thesis was carried out with the purpose of maintaining an existing StepOut mobile application codebase, which was originally developed using React Native technology. The Stepout mobile application is a well-being application which aims to help its users to maintain good health and improve quality of their daily lives. It provides browsing and booking functionalities for the fitness activities of their desire and motivate them to workout frequently. Furthermore, the aim was to develop brand new features for City of Helsinki innovation project. All the new features were delivered within this thesis have made this version considered the StepOut mobile application first Minimum Viable Product (MVP). Those were a subscription package model, a point and rewards system and push notification feature on Android platform. The result of this thesis is a new version of the application which has met the initial requirements, and an overall positive review (80% approximately) from the group of users from the City of Helsinki, who have been experimented with StepOut mobile application and service from the beginning of the innovation project.