I'd like to second Ofir's request for the measure tool. To go with that, I'd love to see a "lock" feature. This would lock the magnifier onto the current position so that it no longer follows the mouse. Ideally, the user could also choose whether the magnifier would continue to refresh.

For examples of the lock and measure features, try Markus Welz's Lens:

http://www.markuswelz.de/freeware/#Lens

I've used Lens a lot for these features. Unfortunately, it lacks great ColorPic features like multi-monitor support and color tools! :)

Thanks for the comment, a good suggestion and if I can squeeze in another checkbox without making the window I'll consider it.

In terms of measurement we have a seperate application for that:

http://www.iconico.com/caliper