Patent ID: 8311480

Claim:
A mobile device system comprising: a plurality of mobile devices associated with a predetermined user, to each of which unique identification information is assigned, wherein each mobile device in the plurality of mobile devices includes a control unit configured to repeatedly execute detection of a misplaced mobile device at a set periodic interval, a storage unit configured to hold the identification information for other mobile devices in the plurality of mobile devices associated with the predetermined user; a location-information acquisition unit configured to acquire location information, a communication unit configured to communicate only with the other mobile devices of the predetermined user, and a group registration unit, wherein, in the each mobile device, the communication unit links location information acquired by the location-information acquisition unit of the each mobile device and the identification information of the each mobile device, sends the information to the other mobile devices, and receives from the other mobile devices location information of the other mobile devices and identification information linked to the location information of the other mobile devices, and wherein, in the each mobile device, the group registration unit detects the other mobile devices located within a predetermined range of the each mobile device on the basis of the location information of the other mobile devices received by the communication unit and the location information of the each mobile device and registers the identification information of the detected other mobile devices as a group.