In a saucepan over medium heat, stir together the white sugar, balsamic vinegar, and pepper. Simmer until liquid has reduced by one half. It should become slightly thicker. Remove from heat, and set aside.
Preheat grill for medium-high heat.
Lightly oil the grill grate. Place peaches on the prepared grill, cut side down. Cook for about 5 minutes, or until the flesh is caramelized. Turn peaches over. Brush the top sides with the balsamic glaze, and cook for another 2 to 3 minutes.
Transfer the peach halves to individual serving dishes, and drizzle with remaining glaze. Sprinkle with crumbled blue cheese.
Can't even describe how delicious these are.