The essays in this book clarify the technical, legal, ethical, and social aspects of the interaction between eHealth technologies and surveillance practices. The book starts out by presenting a theoretical framework on eHealth and surveillance, followed by an introduction to the various ideas on eHealth and surveillance explored in the subsequent chapters. Issues addressed in the chapters include privacy and data protection, social acceptance of eHealth, cost-effective and innovative healthcare, as well as the privacy aspects of employee wellness programs using eHealth, the use of mobile health app data by insurance companies, advertising industry and law enforcement, and the ethics of Big Data use in healthcare. A closing chapter draws on the previous content to explore the notion that people are ‘under observation’, bringing together two hitherto unrelated streams of scholarship interested in observation: eHealth and surveillance studies. In short, the book represents a first essential step towards cross-fertilization and offers new insights into the legal, ethical and social significance of being ‘under observation’.