I travel to SC on a regular basis, so I have to tread the dreaded "DC to Richmond" nest of vipers that the VA police put out. One night, I watched a VA State Police cruiser slowly pull up alongside every out of state plate car on I95 while watching one of these mounted on top of his dash:
This is a Spectre Radar Detector Detector (RDD). Eventually, as he pulled up on a car up ahead of mine, the row of LED's lit up, as did his roof lights a moment later. Another radar detector $100 ticket issued. You would think they would have something more important to do.