Cook the peach wedges in a covered saucepan over medium heat, to get them going. After a few minutes, adjust the heat down to low to prevent them from burning. Stew them a little or a lot until almost to your preferred firmness.
Add most of the blueberries during the last few minutes of cooking. Then turn off the heat and let rest, covered, for a few minutes. (This covered rest helps release the natural syrup that the fruit has made from the side of the pan, allowing you to easily scoop up every last bit.)