Bluetooth is a technique which has been used for transmitting data at short range since the 1990s. Recently, there has been a boom due to the spread of smartphones and beacons. By the way, the Bluetooth logo is based on Old Norse runes, which refer to the Danish King Harald Bluetooth. Bluetooth for example enables data transmission between computers and smartphones, but it can also connect devices with cable-free speakers, keyboards and computer mouses. Bluetooth Low Energy (Bluetooth LE, BLE) has the same range as classical Bluetooth (10-30 meters indoors), but is much more energy efficient. Walls and metal elements cut back the signal strength significantly. Other electrical devices or networks normally don’t have negative influence. Beacons can also be used for indoor navigation and indoor positioning.