Shawn:

Good idea, but in the case of a meter somewhat more difficult.
It will take a vco (voltage controled oscillator) instead of just a buzzer.
There are several articles on this topic in qst.

In particular, March 1997 "a relative indication audible meter reader"

This is the circuit  I am planning to build for my military tube gear.

It looks like a relatively simple circuit to build, and maybe $20 or so 
worth of parts.

If the author is still on the list, do I have your permission to send to 
shawn, or could you send along to him?
hope this helps.