Bring sugar and water to a boil in a medium saucepan, stirring until sugar dissolves. Add peaches and rosemary, and bring to a simmer. Remove from heat. Cover, and let cool. Discard rosemary. Peel peach slices if desired. Transfer peaches with syrup to a container; cover, and refrigerate for at least 1 hour or overnight.
Place 2 peach slices and about 1/4 cup syrup in 8 ice-filled glasses. Add 1/2 cup wine to each; top with club soda. Garnish each with a rosemary sprig, and serve immediately.