Mobile Health Rehabilitation for COVID-19 Recovery

Inclusion Criteria: * Primary diagnosis of COVID-19 requiring hospital admission * Discharged or expected to be discharged directly home from the hospital (not to a skilled nursing facility, inpatient rehabilitation center, or long-term acute care hospital) * Able to ambulate with or without a gait aid prior to hospital discharge * Age ≥ 18 years Exclusion Criteria: * Hospital discharge \> 60 days unless readmitted to hospital in first 30 days, then 60 day window restarts and new exclusion is last hospital discharge \> 60 days * Not ambulating independently prior to COVID-19 illness (use of a gait aid permitted) * Functional impairment resulting in inability to exercise at baseline * Inability or unwillingness to comply with the study requirements or unable or unwilling to follow coaching via mobile-health iPhone interaction * Any absolute contraindications to exercise, including but not limited to: * Recent (\< 5 days) acute primary cardiac event * Unstable Angina * Uncontrolled dysrhythmias causing symptoms or hemodynamic compromise * Uncontrolled hypertension over 255 mmHg Systolic or 155 diastolic blood pressure * Symptomatic aortic stenosis * Uncontrolled symptomatic heart failure * Acute myocarditis or pericarditis * Suspected or known dissecting aneurysm * Any adverse changes during GXT (i.e., persistent oxygen saturation drop below 88% while on prescribed oxygen therapy or significant hypotension such as mean arterial blood pressure \< 60 mmHg on 2 consecutive readings within 1 minute) * High risk for non-adherence as determined by screening evaluation * Any condition, including cognitive impairment, that, in the judgment of the investigator, precludes participation because it could affect subject safety or ability of subject to complete the study * Pregnant