I have operated from fields that have had similar devices. In fact Kbay has lights set up to flash and warn pilots if the gates are up, and cars are driving across the runway (Mokapu Road). It is one more item in the scan, that you should be doing anyways. Last thing I want is a runway incursion while I am on the roll or landing. Edited post: As boom said, air traffic density is way up, and many times both the aircrews and the controllers aren't on their A game.
For what its worth, if you AREN'T skeptical of directions and clearances given to you, and double check them, you are more than likely going to get yourself and your crew killed, or damage an aircraft in your career. I have recently had 4 instances of ATC doing their best to kill me in the terminal environment, one resulted in a HATR from me and the ATC controller getting fired, and the others involved some heated conversations on the ground afterwards. Good SA, scan, CRM and the associated decision making, ie, "Did what the controller say make sense?" is what it is all about... and to steal from A4s: BELIEVE IT!
John