US Patent 10149109 Wearable device detection

A computer-implemented method includes, by a first terminal device among a plurality of terminal devices in a vicinity of a user, receiving a frequency of coexistence from each of one or more second terminal devices among the plurality of terminal devices. The first terminal device and each of the second terminal devices each store a frequency of coexistence, wherein the frequency of coexistence shows a frequency that a terminal device which stores the frequency of coexistence and each of one or more other terminal devices coexisted in the vicinity at a predetermined location. The method further includes calculating a mean value of the frequencies of coexistence for each of the terminal devices which are not currently in the vicinity of the user, and, if the mean value is equal to or larger than a predetermined threshold, concluding that a terminal device is not in the vicinity of the user.