Purpose <p>Vasomotor function plays a critical role in blood pressure (<i>BP</i>) regulation and organ perfusion, and its dysfunction is a major risk factor for cardiovascular disease. Despite the clinical importance of early detection, no noninvasive, quantitative, and widely accessible method for evaluating vasomotor function currently exists. To address this gap, we propose a novel smartphone-based technique for assessing vasomotor activity by measuring fingertip arteriolar elasticity.</p> Methods <p>A smartphone (iPhone) equipped with green light photoplethysmography (gPPG) was coupled to a detachable fingertip pressurization unit to enable volume-oscillometric measurement of arteriolar <i>BP</i> and elasticity indices (stiffness and distensibility) as functions of distending pressure. Vasoconstriction was induced by cold stimulation to validate the method.</p> Results <p>Thirteen healthy volunteers underwent measurements before and during cold water immersion of the contralateral hand. The method successfully quantified arteriolar <i>BP</i> and elasticity indices, revealing significant increases in stiffness and decreases in distensibility (<i>p</i> &lt; 0.01), consistent with expected vasoconstrictive responses.</p> Conclusion <p>This smartphone-based approach demonstrates feasibility as a practical, noninvasive, and accessible tool for assessing vasomotor activity. With further validation in larger cohorts, it may enable early detection of vasomotor dysfunction and support cardiovascular disease prevention through convenient self-assessment.</p>