We introduce WorkoutBuddy, a mobile-based virtual fitness coach that supports home workouts through AI-powered exercise tracking and real-time feedback. Our system leverages the ubiquity of smartphones to make guided exercise accessible to everyone, including users with limited mobility, older adults, or those unable to visit gyms. Using only a phone's built-in camera, the app detects user movements in real time, providing feedback on repetitions and exercise. No extra hardware or setup is required, drastically lowering cost and effort barriers. The UX is intentionally simple, including tap-to-start, pose detection via on-device models, and multimodal feedback. This demonstration highlights how inclusive design and mobile AI can expand access to digital fitness experiences.