Although direct-to-consumer wearable devices are potentially useful in detecting arrhythmias, clinicians should understand the limitations of these devices and be prepared for the influx of data that will derive from patients. Wearable devices initially used accelerometers to encourage physical activity and assess sleep but recently incorporated heart rate sensors to enable targeted heart rate fitness programs and evaluation of resting heart rates (as an indicator of physical fitness). Most devices estimate heart rate using photoplethysmographic (PPG) sensors that detect changes in tissue blood volume (caused by peripheral pulses) and measure using dedicated photodetectors and light-emitting diodes. Accurate measurements depend on adequate blood flow and skin contact and can be altered by patient or device movement, environmental conditions, and ectopic beats. Although most wearables can display real-time heart rates, retrospective analysis of heart rate trends may be limited and depend on the device and its respective application.