4 pp. / Recently, a number of global positioning system (GPS) devices have been introduced commercially which exploit GPS, transforming frequent measurements of time and location, into an estimate of energy expenditure. This fact sheet reviews how GPS watches (GPS fitness units) measure energy expenditure of individual during physical activity. We list popular GPS watches that are on the market and showed pros and cons of these watches. After our field testing, we decided that Garmin Forenunner 305 is our best pick for the GPS watch. We included information on Geocashing, which is one of popular outdoor activities using GPS receiver or other navigational techniques.