Simply put, http://i54.tinypic.com/24oreax.png
It would use a wand different from the cuboid wand.
Those would be ovoid selections that could be copied, set, outlined, replaced, etc. instead of using a rather imprecise //sphere or //hsphere command.
In the event that the first and second positions would be the same (image on the right), a //radius command could be used to set the radius, thus allowing for perfect spherical selections to be created without the hassle of counting blocks and making sure things are symmetrical. It could work in a similar way as //expand.

I did not include it in the picture above, but if the two positions were to be on the same axis, the distance between the two would be treated as a radius and the first position as the center of a spherical selection.
... or this could be used to make hemispheres.

The only reason I haven't done this yet is because Java makes it difficult to do what I need it to do, but I want to do it eventually.

Moved: http://redmine.sk89q.com/issues/83