Indoor positioning systems and methods including a reverse-beacon for location determination and presence sensing technology. The reverse-beacon is any device comprising a transceiver and a computer operating with system nodes and will generally be in the form of a smartphone or other mobile computer. The systems and methods utilize wireless signals of any device that adheres to a general-purpose communication protocol, such as Bluetooth™ and Wi-Fi, to provide location-based services such as location determination and acting as a ground-truth field for presence sensing systems. The systems and methods operate by passively licensing to wireless communications that take place during the ordinarily course of operation of a wireless network irrespective of the presence of the reverse-beacon.