Our Posifon Nano and Pico Pro devices have the function that in addition to GPS, they can also pick up positions via wifi, ie the devices detect mac addresses nearby. The standard for Wi-Fi in Europe is a general range (the signal strength of routers and antennas has a limited output power due to the rules for CE marking) that allows you to reach the network in a radius of up to 50 meters indoors and 100 meters outdoors. Then the range is affected by the number of walls and other obstacles present, the material they are made of and so on. So the range can effectively be reduced to just a few meters indoors.