 The study aimed to assess the accuracy of heart rate measurements taken by a Motorola Droid smartphone when compared to electrocardiogram, ECG, and known in 9560BT pulse oximeters. The results showed that the Droid provided valid heart rates at varying levels of movement-free mental perceptual motor exertion. This suggests that the Droid could be used in mobile cell phone-delivered health promotion and wellness programs. However, further validation is needed to determine its applicability while engaging in physical movement-related activities. This article was authored by Matthew J. Grigowski, Martina Mueller, Alexei Vertigel, and others.