The idea is a survival horror game, right? And you can enter a mode where your senses are enhanced. Maybe items you can interact with get a sort of aura, some metaphorical-type stuff happens like maybe a killer has bloody hands or something, I dunno, and there's no direct cost in the sense of a meter going down or whatever. But the scary shit gets even scarier, because you're seeing partway through the Veil, and maybe there's a good game-mechanical way to reflect the whole "nothing seen with the Sight can ever be forgotten" thing. Increased SAN damage, maybe? Or bits of stuff you see with the Sight start drifting around the screen like afterimages, even when it's off? Interface screws?
I dunno, I'm not a game designer. Just think it could be cool.