Beacons have boomed since 2013 - when Apple introduced its iBeacon standard. 2015 Google followed with Eddystone. Today, there are many beacon suppliers on the market.
For indoor navigation purposes, beacons are placed at regular intervals in the building. They then regularly transmit signals via Bluetooth that are received by mobile devices (e.g. smartphones). An app on the smartphone interprets the signals and the position is determined directly on the end device. Beacons cost between about three and 30 euros, have battery lives of several years and can cover up to 30 meters indoors. How many beacons are needed in a building depends on the size of the area and the desired positioning accuracy.