Hi, BIG dials are cool...
I have made some with simple materials also.. Foamcore board and foamcore pointer for example. Or cardboard. Or ???
If you balance the pointer (equal weight to left and right of pivot point) even small servos like those below will work. So only one Arduino pin needed per dial. (The straw stuck on the standard servo arm in the photo is so light it's No Problem).
Here's an example sketch that you could use to test.. It uses a potentiometer which you can turn by hand to see the servo action follow it.http://arduino-info.wikispaces.com/YourDuinoStarter_ServoPotPosition
See the Map function in that code. You could figure out how to map the parameter you want to "Meter" to servo movement. Maybe output the servo data to Serial Monitor and 'calibrate' the marks you make on the dial. See: http://arduino.cc/en/Reference/map
DISCLAIMER: Mentioning stuff from my own shop... but you can get these lots of places..http://goo.gl/Ys5pp