ANPR is used in many practical ways. Number plate text detected in images is simply just data to a computer. Data can be applied to computer logic to perform various tasks. For example to compare against lists of known plates (existing hotlists like the NP Tracker suspicious vehicle numberplate database) and raise a boom, open a barrier, sound an alarm, send a notification or just to record the text, date, time, location and images for later viewing and reporting.
Download Raspberry pi image here and build your own ANPR system.