I just discovered MaxCurve and it's totally awesome!!!! Curve tool for RGB and LAB colorspace!!!! also has has interesting curves for contrast, exposure, gamma, temperature, lightness, and B&W. It also has an interesting HSL curve tool!!!! also has extensions!!!!
If you are a curve freak like me, you must get this!!!! it's totally awesome.
MaxCurve - Curve tool & image editor for pro photography by Xiaodong Wang
The extension is non-destructive!!!! i can hit done and come back to edit with the extension at a later time and my curves are still there and i can change it. It's non-destructive until i edit the photo with another app which causes the edits to be burned in. So it's not completely a Special Object (using Photoshop lingo).