Help with a gin & grapefruit recipe?

I'm having some friends over and want to do a speed infusion with my ISI whipper. I want to take some gin I have and infuse it with grapefruit. I plan on using the whole grapefruit, pith included, to get all the favors.Any recommendations on what to do with such a gin? There are plenty of gin and grapefruit juice recipes out there, but not when the gin is infused that way. http://www.reddit.com/r/cocktails/comments/3f170p/help_with_a_gin_grapefruit_recipe/