Start this ahead while you are grilling other courses. Line bottom of heavy skillet to protect from soot. Add wine and sugar, slit vanilla bean open lengthwise and scrape out seeds with tip of pairing knife, adding these (and entire vanilla bean) to wine mixture. Allow mixture to boil on the grill until it becomes reduced to about 1/2 cup and has a slightly syrupy texture. Set aside until needed.
Procedure for Pears:
With a pairing knife, slice the bottom of each pear half into 1/2 inch thick slices (about 2/3 of the way towards stem, leaving the stem end intact.) Fan the bear slices slightly to make a flatter grilling surface. Remove vanilla bean pod from syrup. Dip each pear half in syrup, place on grill, flesh side down, and grill just until pears are lightly grill-marked. Turn pears skin-side down and continue grilling until skins are lightly grill-marked. Remove from heat and set aside. To serve add half of the remaining wine syrup and stir well to blend. Spoon a bed of the ricotta mixture on individual serving plates. Fan a grilled pear half on top of ricotta, drizzle with remaining wine syrup, sprinkle with black pepper and serve.