Leveraging miniaturized sensor and monitoring technology integrated in easy-to-wear wristband wearables represents a great opportunity for advancing Resilience and Mental Health of e.g. employees that experience high workload. Therefore, it is important to gain insights into the reliability of such technology before far reaching conclusions can be drawn and interventions can be developed. To that aim, we tested three wearable wristband sensor systems (Apple Watch, Microsoft Band and Fitbit Surge) and compared the assessed sensor output with a reliable ground truth. The results showed that heart rate, steps and distance varies considerably around the ground truth during tasks that required body movement. However, during the rest condition (sitting on chair) the heart rate was considered more reliable. It is concluded that caution is warranted while using and interpreting physiological data assessed by the new technology, but, in rest (e.g. pauses, sleep) the wearable' sensors could be used to detect undesirable physiological patterns, indicative of threats to resilience or (mental) health. © 2016 IEEE.