This is a Bluetooth Low Energy (BLE) demo using the RL78/G1D microcontroller. It runs on an extremely small amount of power, so data communications can be performed for a long time on a battery. In this demo, you can see that you can select from among three slave devices (text data, temperature data, or illumination data) for one master device using a smartphone. You can also see that you can check the temperature of a refrigerator, whether the door is open or closed, and other operating statuses from anywhere via the Internet.