Comment by raziel2701

This was a common mechanic in the splinter cell games, you'd wait for a guard to go through a door with a keypad and you'd put on your thermal vision goggles to find the 4 numbers. I guess that now that thermal cameras are becoming more ubiquitous this has jumped closer to reality. Back then I can't imagine there were thermal cameras that were small and cheap. Nowadays you can get a flir lens for your phone at about $200 - $300 if I recall correctly.