There has been a rapid proliferation of AI-based medical devices and Software as a Medical Device (SaMD), largely due to their ease of deployment and scalability. Despite these advantages, many such technologies face limited clinical acceptance and reduced effectiveness in real-world healthcare settings. This gap is frequently attributed to technology-driven development approaches that insufficiently involve end users and other key stakeholders. This paper describes a structured co-design approach applied to the development of NCare, a smartphone-based SaMD designed to monitor motor symptoms associated with Parkinson's disease. Co-design engaged people living with Parkinson's Disease, clinicians, developers, and commercial stakeholders in iterative system refinement. Workshops, surveys, observational methods, and a trial phase were used to capture experiential, clinical, and contextual insights across different stages of development. This approach enabled the identification of usability challenges, workflow integration requirements, and reporting requirements absent from developer-led approaches. The paper presents a case study of co-design protocol intended to support the development of needs-driven, clinically relevant, and adoptable digital health technologies. Method Overview: Engage multiple stakeholder groups across stages of device development. Use iterative co-design activities to elicit experiential and practice-based insights. Apply feedback-driven refinement and trial deployment to assess real-world usability and implemen-tation considerations.