I believe this is one for the developers, making a new gauge and put it in an overlay.
Looking at the bugs they have to fix to get VIRB Edit to work on all PC's and with all graphic cards, I expect this will not be high on their to-do list.
Didn't know we already had such an overlay, will also have a look at that :D
Well, the Mac developers may have time to do it, since they don't have those problems. :-)
Yeah, i added time to one of my cycling overlays, and it wasn't difficult.