Infrared: Here infrared light pulses are used to locate signals inside a building. A professional installs infrared readers in every room of the house, and when they create a pulse, the pulse is read by a reader device. When properly installed, this system is highly accurate. Unfortunately, you have to install a reader in every room, which can be expensive if you have a large building.
Wi-Fi based tags: This technology relies on Wi-Fi transmitters that send simple packets to Wi-Fi access points in a building. The access points report the time and strength of the readings to a backend that makes use of algorithms to calculate the position of the various objects and persons.