Research Impact Summary: In 2016 the most popular Christmas present in the USA was the fitbit. These wearables measures physical activity and are designed for the consumer to use for various purposes depending the product specification. The common feature of these are the dual use of a watch with physical activity tracking and the potential for socialising results. Thus, wearables and apps, which are used for measuring physical activity, have potential for promoting health enhancing physical activity. However, the use case of adolescents is not as straight forward as it has been for adults. Therefore, we have been interested in the potential behind physical activity trackers (PAT) among adolescents and to do this, we need to know what is the prevalence of ownership and use of PAT. It is important for survey items that feature in monitoring surveys such as the Health Behaviour in School-aged Children – WHO collaborative Cross national (HBSC) study have been tested scientifically for validity. One type of validity is testing the reliability of the item. This study examined the reliability of items related to PAT. As a result of the study, there was moderate agreement for the items on apps and heart rate monitor/sports watch. Therefore, the items can be used in future monitoring studies to indicate the prevalence of PAT among adolescents.