With the smartphone revolution comes an increasingly powerful new set of tools to reduce our use of doctors, cut costs, speed up the pace of care, and empower patients. Soon, we will be wearing attachments to diagnose ear infections or track heart rhythms and using apps to monitor our mental health. Digital avatars won’t replace physicians, but the relationship will be radically altered. We’ll be able to do routine diagnoses and monitoring (lab tests, physical exams, sensors, and some imaging) on demand. Wherever a mobile signal is available so, too, is the promise of marked health improvements. What are the benefits and risks of this bottom-up inversion of healthcare? Is it really the most profound shakeup in the history of medicine?