Perez MV, Mahaffey KW, Hedlin H, et al. – Researchers assessed the ability of a smartwatch app to identify atrial fibrillation during typical use. Over 8 months, they enrolled more than 419,000 participants who did not have atrial fibrillation and used a smartphone app to consent to monitoring. Among the participants, 0.52% were notified of irregular pulse during a median of 117 days of monitoring. Among individuals notified of irregular pulse, 34% and 84% had atrial fibrillation on following ECG patch readings and notifications were concordant with atrial fibrillation, respectively. This siteless (no on-site visits were needed for the persons), pragmatic study design offered a foundation for large-scale pragmatic studies in which outcomes or adherence could be probably evaluated with user-owned devices.