The rise of digital health has provided new opportunities for patients to be more actively involved in their health and wellbeing. Despite the increased use of mobile health apps, there is still a lack of research on patient self-monitoring, and few studies have focused on children with chronic diseases and their parents. In this study, we draw from a case of the design of a mobile application – a symptom tracker – to continuously monitor children with periodic fever and the theoretical concept of boundary objects, to understand the role of digital artifacts in current healthcare practice. The research approach is qualitative, building on interview data with parents and experiences from the co-design process involving researchers, physicians, and other key stakeholders. The aim of the paper is to contribute with a better understanding of how an app for tracking children’s fever (a symptom tracker) can support the pediatricians as well as the parents and their children during the treatment process. The research question is: In what ways can a symptom tracker increase stakeholder involvement and how may this affect their relationship boundaries and collaborations? Our findings suggest that the symptom tracker can be seen as a boundary object that binds the children, parents, and pediatricians treating them by connecting the app to the context of both the patients and healthcare practice. We argue that such an object (symptom tracker) can function as external support and, thereby, an essential part of the treatment process.