Hypothermia is a state where the body cannot balance the body heat due to excessive cold temperature pressure so that there will be loss of heat in the body. The result will be a quickly decreasing body temperature. A condition where a body temperature is less than 35°C and that it is accompanied by a decrease in consciousness may cause a death threat. Hypothermia is more common when climbers perform activities in cold temperatures and strong winds, and when they wear wet clothes. It is not easy for a mountain climber to find out his own body temperature as well as that of his friends and to determine whether the body temperature is safe or affected by hypothermia symptoms. Therefore, this research formed a device to detect hypothermia. It consists of temperature sensor, pulse sensor, and accompanied by heating elements based on wireless body area network (WBAN). This device will connect to the user's smartphone by using Bluetooth, so the user can see the condition of his body, adjust the temperature of the heating element, and make a group of climbers. The experiment result shows that the device can detect hypothermia symptoms and inform these symptoms to the users and groups of mountaineers in WBAN area, and the climbers can be more vigilant in responding to hypothermia so that mortality cases caused by hypothermia can be minimized.