Inclusion Criteria:  Fluent in written and spoken English Already enrolled in the Remote Hypertension Program Average of last 3 office blood pressures >140/90 mm Hg in last 18 months OR Last office blood pressure >140/90 mm Hg in last 6 months OR Referred by MD and last 1 blood pressure >130/80 mm Hg Own an iPhone  Exclusion Criteria:  Tachycardia (heart rate at rest > 120bpm) Atrial fibrillation, persistent Severe heart failure (LVEF<35%) Pheochromocytoma Raynaud's disease Trembling and shivering Known pregnancy Breastfeeding Arteriovenous fistula Arm amputation Exfoliative skin disease Lymphoedema Known allergy to silicone Not Massachusetts resident Last MGB office visit >3 years No-MGB provider Terminal medical condition CKD 4-5 (eGFR ≤ 30 mL/mn)