The chapter is one of several edited and refereed outputs based on the project 'Ere be Dragons. This is a unique pervasive game/artwork which uses both GPS and live heart-rate monitoring in a mobile device. The objectives of the game’s development include a health science agenda concerned with the player’s wellbeing and physical activity, reflecting increasing concern over the health consequences of modern ways of living. These issues are explained, and the technical, design and gameplay challenges in working with heart rate data are described. An arts-based approach to mapping the exploratory aspects of a game is introduced, emphasising the relationships between objective and subjective aspects of the player’s experience.