"Camera undo" allow to undo and redo the camera transform for each camera.
Like in Maya (and other software), now you have the option in blender to 'ctrl z' your camera location.
To undo the camera transform, press 'Ctrl + Alt + Z', and to redo, press 'Ctrl + Alt + Shift + Z' .
For example - If you move the camera 4 times, and then you move another objects or continue to animate your rig. At any point you can select again your camera, and undo your 4 (or more) transform changes (normal undo will undo the animation or other objects movement, and not only the camera).