mHealth apps are mobile device applications intended to improve health outcomes, deliver health care services, or enable health research.1 The number of apps has increased substantially, and more than 40 000 health, fitness, and medical apps currently are available on the market.2 Because apps can be used to inexpensively promote wellness and manage chronic diseases, their appeal has increased with health reform and the increasing focus on value. The bewildering diversity of apps available has made it difficult for clinicians and the public to discern which apps are the safest or most effective.