In the UV editor, there is a selection type called “Active Face Select”. It’s not exactly what you’re looking for, but if you select only face in the editor or viewport, it’ll show it as individually selected (i.e. you can tell which one is the one you’ve just selected).
UV-mapping doesn’t work that way. Sure, you can have separate images all mapped to the same UV coordinates, but you can’t have separate UV coordinates for the same mesh. Scale your UV layout to be large enough to deal with it. Also, make use of the zooming capabilities in the UV editor, as well. The brush select – B (for Box select) and B again (for brush) – will also help in your selecting UV coords. You can alter the size of the brush with your mouse’s wheel.
I hope that helps,