This paper proposes a service for elderly people suffering from dementia. The service does not require new infrastructure, and is accessed by commonly available smartphones. One of the key advantages of this system is that it uses a very small sensor and BLE technology which makes it both small and energy efficient. An application installed on smartphones will allow for city dwelling dementia sufferers to be tracked for the purpose of assisting them. The authors conducted a social experiment in Aichi Prefecture, Obu City on November 29, 2014. There were forty participants who searched for sensor carrying elderly people suffering from dementia. The results of this social experiment confirm that this technology will help to find elderly people with dementia, and also provided some additional findings as well: 1) During times of rainfall, the detection range of the sensor decreased from 10m to 5m 2) detection from the rear had more narrow coverage that from the front, because of the interference of the human body blocking the transmitted signal, and 3) then the smartphone was operated within an automobile, it could not reliably catch the transmissions from the sensor.
