BACKGROUND: Telehealth and other technologies that enable remote patient-physician communication technologies have widespread use among physicians and other health care providers, but the impacts of these technologies on physician productivity are not well known. OBJECTIVE: To determine whether a HIPAA-compliant application that allows physicians to call patients from their personal cell phones is associated with an increase in physician productivity. DESIGN, SETTING, AND PARTICIPANTS: We used a 100% sample of Medicare claims and longitudinal physician-level data to examine whether physician use of a smartphone application that enables physician-patient phone calls is associated with changes in Medicare patient volume and services. We compared early adopters of the application, 31,577 physicians providing Part B services who initiated use of the application between January 2014 and December 2017, with later adopters, 22,988 physicians who initiated use between January 2018 and July 2019. MAIN MEASURES: Physician productivity was measured as total Medicare Part B beneficiaries, total Part B services provided, the number of Part B beneficiaries with any evaluation and management (E&M) service, the total number of E&M services provided, and the average number of E&M services provided per beneficiary. KEY RESULTS: Following application use, there was a 0.52 increase (95% CI: 0.19 to 0.85) in the monthly number of Part B beneficiaries seen. This difference translates to a 0.8% increase in Part B beneficiaries. Similar increases were observed for the number of unique beneficiaries for which the physician provided E&M services-a 0.50 increase (95% CI: 0.27 to 0.73) or 1.2%. There was a 0.43 increase (95% CI: 0.07 to 0.78) in monthly E&M services (0.7% increase). CONCLUSIONS: Physicians who used a freely available smartphone application modestly increased their total Medicare beneficiary volume and total number of E&M services provided, suggesting potential improvements in physician productivity.