Grid Coordinates

Sometimes maps are asymmetrical, but at other times we want objects placed symmetrically on different sides of a given map.

With that in mind, would it be possible to add coordinates to the grid, down to the pixel that verify where objects are being placed? Bonus if it counts the exact center of the map as (0,0) so that you can easily tell that you're placing the object in the right area (for example, one at (120,30) and the second at (-120, 30)).