One of the hardest parts of maintaining a WiFi system is keeping track of who's on your system, and what they're doing with it. Yet this is also one of the most crucial aspects of WiFi management.
There have been tools available for years which help WiFi administrators try to keep track of networking devices on their system, but there were no real magic-bullet solutions. Usually, your best bet was two combine two or more tools, such as a network scanner along with a packet-sniffer, and try to correlate the results based on IP or MAC address. However, this is often imprecise, as well as being difficult to do quickly or easily. The only other viable option was expensive pieces of dedicated hardware.