I haven't read The Frequency, but when I was looking at the preview page with the cryptic-looking hex map of the city, my initial thought was that it was some kind of tool to keep track of where the Character was in 'tuning'. A kind of visual representation of dimensional frequency space, if that makes sense. So one of the concepts I'm rolling around right now is using hex maps to map non-physical things. I'm starting to wonder if it's one of those ideas that sounds cooler in the abstract than in any concrete implementations, though.