There have been several attempts from meterologists to extract wind data from through the actual and target direction values.
Other sites use it to locate GPS-jammed areas because ADS-B can indicate when the reception fails (but still is able to transmit its position due to inertial fallback mechanisms).
AMDAR: https://madis-data.ncep.noaa.gov/MadisAircraftPublic/
AIREP: Go to https://www.1800wxbrief.com/Website/interactiveMap, turn on the "Pilot Reports" layer, and look for "ARP" symbols on the map. You'll mostly see these over oceanic routes, especially in the Atlantic.
The AIREP reports are coded in PIREP format, so you'll need to look up the instructions for manually decoding those online.
They partially replaced the data with the experimental Aeolus satellite which made its data into the productive forecasts within months due to their high quality.