Hello you great CHDK people, as my first post I'd just like to voice my appreciation to all the people who've made CHDK such an awesome app!
I am into large format photography, and I had the idea of using my sd880 as lightweight and potentially very helpful spotmeter. Well, actually, after finding out about CHDK I decided to get myself little compact so I could play with CHDK on it... and potentially use it as a spotmeter.

So, I did some tests of EV values from my ixus in spotmetering mode vs my Minolta Spotmeter F and found the values to be close enough for practical use (usually a difference of less than 1/3 stop).
From there I worked out the maths for converting the camera's EV value into an F-Stop given a particular iso and shutter speed. I was thinking of just writing a script to do just output the info to screen, but though it would be better if I could get something on screen that looks something like the display of my spotmeter. So I checked out the CHDK source code and was suprised at how easy it was to get everything compiling and running. Awesome set up! Especially the CHDK Shell!
So far I have I new OSD element displaying all of the info that I want (EV value, current ISO, shutter speed and the resulting F-Stop on a scale of F-Stops). It can also store multiple readings and show them on the scale so one can work out zone system type stuff. It looks like this:

The last remaining hurdle is to have an easy way to change values. The ability to quickly scroll through shutter speeds as well as being able to tell the camera when to store values / clear values. After thinking about this, I decided the best way would be to write a scipt, similar to the Tv Mode script that is included in CHDK, and give it hooks to be able to change the OSD spotmeter values. I am currently working on getting a script set up.
I was wondering if anyone had any opinions on this? Better ways to do it etc? And if there is anyone else who would find something like this useful? If so I would be keen to try and get my stuff (once its all working) into the main build, or some other place where is accessible to people. I don't know what the process is to get stuff checked in? Can anyone do it?