Effective documentation of pain dynamics and medication use remains a challenge in palliative care, largely due to limitations in routine data collection and the lack of interoperable digital solutions. This study presents the design and initial development of a mobile health application to support structured pain assessment and medication management in palliative care. The system integrates standardized clinical instruments, including the Visual Analog Scale (VAS) and the Brief Pain Inventory (BPI), and was designed following principles of user-centered design, modular software architecture, and information security in compliance with the Brazilian General Data Protection Law (LGPD). The application was developed using the Flutter framework with Firebase as backend infrastructure, enabling cross-platform operation and secure data management. Interoperability with Electronic Health Record systems is supported through HL7 FHIR standards. The methodological approach follows the System Development Life Cycle (SDLC), and future stages include usability evaluation based on the Technology Acceptance Model (TAM). The proposed solution aims to improve clinical communication and monitoring in palliative care while promoting an accessible, secure, and human-centered digital health approach.