Step 1In a large sealable plastic bag, such as a Ziploc freezer bag, combine the peaches, sugar, wine and rose geranium leaves (or vanilla or cinnamon, if using). Squeeze out all of the air and seal tightly.
Step 2Bring a large, wide pot of water to between 140 and 150 degrees and reduce the flame to the point it will maintain that temperature. Lower the tightly sealed plastic bag containing the peaches into the water and cook, maintaining a steady temperature. Keep a cup of cool water beside the pot and if the water in the pot gets too warm, add about one-quarter cup to cool it down. The first 5 minutes or so will take some adjusting, but after that it should maintain the temperature with a minimum of fuss. Cook for 45 minutes.
Step 3Remove the bag from the water. Pat the bag dry to avoid diluting the juices and empty the peaches into a bowl (discard the cinnamon stick, if needed). Serve at room temperature, dividing the peaches and sauce as desired among each serving.