As healthcare data becomes increasingly personal and pervasive, we face a critical challenge: how do we harness this information for better care without sacrificing trust or privacy? In this talk, Dr. Oshani Seneviratne presents a series of systems that bring together decentralized AI, knowledge graphs, and explainability to enable personalized health applications. From real-time emotion monitoring using on-device learning, to auditable clinical decision support encoded as smart contracts, and nutrition-aware recommender systems built on semantic food knowledge, their work bridges patient-centered insights and clinical accountability. These approaches aim to redefine how we deliver intelligent, secure, and transparent healthcare at scale.