Here's the (probably) most famous mask in the world from the inside, which you can barely see in the movies. Lord Darth Vader's mask is supposed to help him breathe, but what do all those other little electronic parts do?
Monitor his state? Give him physical feedback about his environment? Amplify his powers? Pick his nose? Facial massages? Shave him? I think I'm going with scratching his face when it gets itchy. It makes perfect sense. [Walyou]