Mobile and smartphone (mHealth) technologies have the potential to improve diabetes care and self-management, but little is known about their effectiveness and how patients, providers, and payers currently interact with them. We conducted a systematic review and found only 20 peer-reviewed articles, published since 2010, with robust evidence about the effectiveness of mHealth interventions for diabetes. The majority of these interventions showed improvement on primary endpoints, such as HbA1c; mHealth technologies that interacted with both patients and providers were more likely to be effective. There was little evidence about persistent use by patients, use by a patient's health care provider, or long-term effectiveness. None of the studies discussed regulatory oversight of mHealth technologies or payer reimbursement for them. No robust studies evaluated the more than 1100 publicly available smartphone apps for diabetes. More research with valid study designs and longer follow-up is needed to evaluate the impact of mHealth technologies for diabetes care and self-management.