What I don't understand is why the App needs the info, wouldn't it make more sense to change the API so it's just a call to /users?near={co-ord} and a simple list of users is returned without any location information? Sure you could still triangulate by using fake accounts and guestimating the boundaries based on when a user is and is not returned in the list…

EDIT: Ah, just fired up tinder, and saw the "x kilometres away from you" forgot about that haha :D