I believe we need (desperately) a tracking ability.
with so few players in the world...and with talk of expanding it...we need it for both offensive and defensive purposes.
offensive. tracking 'prey'. hunting other players, whether for good, or bad.
defensive. watching your surroundings to keep track of potential interlopers.
without some means to locate one another, it's either a game of wait, and wait, and wait, or one of just wandering about aimlessly hoping to bump into something.