An activity visualization device for personal use, said device being adapted to be used in close physical contact with an individual, and said device at least comprising: - an accelerometer configured to measure the physical activity of an individual, - a memory configured to log said physical activity over time, - a processing unit configured to carry out computational operations on the basis of measured and/or logged data, and - a visualization display configured to present the measured and/or logged data, or data resulting from the computational operation thereof, wherein said device adopts the shape of a watch, and wherein said display is adapted in such way that it comprises a dial covering a given period of time, wherein physical activity data or data resulting from the computational operation thereof are displayed as a graph, or curve, over time, characterized in that said device further comprises - a communication means configured to obtain environmental data from an external source, said data selected from the group consisting of: - environmental temperature, - environmental air humidity, - environmental atmospheric pressure, - environmental ozone concentration, - sky cloudiness, - sunrise and/or sunset data, - environmental light intensity, and/or - environmental light spectrum, and - an analysis unit configured to calculate recommendations for said individual with respect to physical activity and/or environmental light exposure based on the measured data and/or one or more of said obtained environmental data, wherein said display is configured to display the calculated recommendations by means of overlaid circular segments on the dial, wherein said display is configured to display personally recommended levels of physical activity, to display personally recommended sleeping times, to display times when exposure to light should be avoided, or sought and/or to display times when food intake should be avoided, or carried out. - an accelerometer configured to measure the physical activity of an individual, - a memory configured to log said physical activity over time, - a processing unit configured to carry out computational operations on the basis of measured and/or logged data, and - a visualization display configured to present the measured and/or logged data, or data resulting from the computational operation thereof, - a communication means configured to obtain environmental data from an external source, said data selected from the group consisting of: - environmental temperature, - environmental air humidity, - environmental atmospheric pressure, - environmental ozone concentration, - sky cloudiness, - sunrise and/or sunset data, - environmental light intensity, and/or - environmental light spectrum, and - an analysis unit configured to calculate recommendations for said individual with respect to physical activity and/or environmental light exposure based on the measured data and/or one or more of said obtained environmental data, - environmental temperature, - environmental air humidity, - environmental atmospheric pressure, - environmental ozone concentration, - sky cloudiness, - sunrise and/or sunset data, - environmental light intensity, and/or - environmental light spectrum, and - an analysis unit configured to calculate recommendations for said individual with respect to physical activity and/or environmental light exposure based on the measured data and/or one or more of said obtained environmental data,