1. An inventory management system, comprising: an inventory holder including inventory bins configured to store inventory items; three fixed radio frequency (RF) antennas transmitting RF interrogation signals and receiving RF response signals generated in response to the RF interrogation signals; a user-wearable unit configured to be worn in proximity to a user's hand, the user-wearable unit including a portable radio frequency (RF) transceiver configured to transmit the RF response signals in response to receiving the RF interrogation signals; an RF transceiver operatively coupled with the three fixed RF antennas; and a management module operatively coupled with the RF transceiver and configured to process signals generated by the RF transceiver to: continuously determine a location of the user-wearable unit in a three-dimensional space; and monitor performance of an inventory task assigned to the user by continuously comparing the location of the user-wearable unit in the three-dimensional space with one or more locations of the inventory bins in the three-dimensional space to detect an interaction between the user and one of the inventory bins, the inventory task assigned to the user being at least one of retrieving an inventory item from a designated inventory bin or placing an inventory item into the designated inventory bin.