RecruitingBehavioural interventionReach Out 2: Emergency Department-Initiated Hypertension Mobile Health Intervention Connecting Multiple Health SystemsEmergency department visits provide an opportunity to identify people with undiagnosed, untreated, or uncontrolled high blood pressure. In Reach Out, we will test whether a mobile health intervention yields a greater reduction in blood pressure than usual care among individuals identified with high blood pressure during a safety-net emergency department visit. Subsequently, we will estimate the reduction in heart attack, stroke, and dementia if Reach Out were implemented across all U.S. safety-net emergency departments.