I thought the Geoscape debug mode already did that.
There's a debug mode?
edit:
You enable it by opening options.cfg and making this string be:
debug: true
then on geoscape you hit CTRL-D several times to cycle through modes.
There are three modes.
NONE: Doesn't display debug areas.
REGIONS: Shows regions -- the areas used for scoring performance, e.g. "North Atlantic".
COUNTRIES: Shows the countries -- their areas used for scoring performance.
(see attachments)
EDIT II -- doesn't appear to be any way that returns the LON and LAT of where the cursor is hovering over.