Preheat grill to medium. Brush peach halves with coconut oil.
Grill peaches cut side down for a couple of minutes, or until you have nice grill marks. Flip over, and grill for about 2-3 minutes, or until fruit is tender.
While the peaches on the grill, prepare the blueberry syrup. In a medium saucepan, combine the blueberries, lemon juice, honey, cinnamon, and butter. Over medium heat, bring to a boil and then let simmer until sauce is thickened.Using the back of a wooden spoon, mash a few of the berries against the side of the pan so they burst open.
Once the peaches are grilled, remove to a serving plate and spoon blueberry syrup over them.