Popular health apps are commercial services. Despite the promise of empowerment they offer, the tensions introduced by their data-driven, dynamically adjustable digital environments engender a potential for manipulation to which their designers and operators can easily succumb. In this important book, the author develops an ethical framework to evaluate the commercial practices of for-profit health apps, proceeding to a detailed proposal of how to legally address the exploitation, for financial gain, of users' need for health. Focusing on the intricate tracking of users over time, coupled with the possibility to personalize the environment based on knowledge gained from tracking, the book's in-depth analysis of popular for-profit health apps engages with such particulars as the following: the strategic framing of health in health apps; the cultural tendency to presume we are unhealthy until we have proven we are healthy; the key concepts of autonomy, vulnerability, trust, and manipulation; how health apps develop ongoing profitable relationships with users; and use of misleading and aggressive commercial practices. The author argues that the European Union's Unfair Commercial Practices Directive, when informed by ethical considerations, offers promising legal solutions to the manipulation concerns raised by popular for-profit health apps. The book will be welcomed not only for its incisive scrutiny of the health app phenomenon but also for the light it sheds on the wider problems inherent in the digital societywhat digital environments know about their users, how they use that knowledge, and for which purpose. Its progress from an ethical approach to legal solutions will recommend the book to lawyers concerned with business practices, human resources professionals, policymakers, and academics interested in the intersection of ethics and law.