And just to throw some more ideas at it now, lol: Red color when price lowers a lot, orange when it lowers a little, green when it grows. Maybe 24 hour graph if it's not too complicated for the display.
Well, ideas are always welcome, I suppose. And I like the ideas that you proposed. However a 24 hour graph seems a bit to much right now. Maybe as an firmware update later on? I have an idea as well, let the user decide from which source it has to get it's price.