eHealth holds the promise of revolutionizing health care by improving its efficiency; extending and enhancing its reach; energizing and engaging its practitioners and their patients; and in the process, democratizing, decentralizing, and even partially demystifying the practice of medicine. In emerging and developing countries, the use of eHealth and smart health-care planning has the potential to expand access to necessary treatments and prevention services that can serve as underpinnings of rapid economic development. In developed countries, the application of eHealth promises to restructure the business model of health-care delivery, while at the same time improving and personalizing the quality of care received. This article reviews the past, present, and future of eHealth in an effort to illuminate the potential of its impact.