The invention relates to a method for measuring and displaying data linked to a person's physical activity, comprising: measuring data linked to the person's physical activity using a mechanical sensor in a wrist watch worn by the person； displaying the measured data on the watch face； taking an image of the watch face using a camera in an electronic device； analysing the image in order to determine the data； processing the data so as to process the analysed data； and displaying the processed data on a screen of the electronic device.
