Background: Oncology consultations can be overwhelming and information-dense. Consultation audio recordings are an effective method to promote patient participation, improve patients' recall and understanding of medical information, and can increase engagement and support through sharing with family and friends. Innovative m-health technologies such as the SecondEars consultation audio recording mobile app provide a patient-designed and controlled audio recording solution while ensuring security and legal protection for clinicians. To ensure the SecondEars app meets the needs of patients, family, clinicians and hospital administrators, the opinions of stakeholders and end users are integral to the concept and study creation, design, and testing processes. Aim: To use key elements of codesign methodology to develop and test SecondEars, a mobile app that allows patients to audio record their consultations within a clinical oncology setting. Methods: The SecondEars app concept began with consumer suggestions that consultation audio recording be used as standard practice of care using patient-driven (use is controlled/determined by patients) technologies. An app solution was conceived and the concept discussed through engagement of consumers as part of the project and research codesign team. Key health service stakeholders comprising representatives from: legal, information technology (IT), clinical service leads, digital strategy, and health information services (HIS), provided project oversight and core legal and data management requirements. The Scrum management framework was used to structure the codesign process during the development and testing phase. Six workshops were run to facilitate further user input with regard to specific app functionality and design. A wireframe version was developed and tested by the codesign team in the final workshop. Feedback was incorporated into a prototype which was circulated for acceptance testing. Results: Twenty people participated in the stakeholder engagement and workshops, comprising: oncology consumers, researchers, IT, HIS, app developers, and oncology health professionals. Key specifications necessitated that SecondEars be patient-driven, secure and confidential, have clear legal guidelines regarding audio recording sharing, be integrated with medical records, and require minimal upfront and ongoing resources. Seven people tested the prototype app during user acceptance testing and gave positive and constructive feedback. A final version of the app was then made available for clinical testing. Conclusion: The SecondEars consultation audio recording app has been successfully created by and for patients. This app gives patients permission and autonomy to audio record and share their consultations responsibly, while maintaining legal protection for clinicians. This app is currently being tested in a clinical setting prior to conducting an implementation study.