Heat the wine and sugar in a medium saucepan over medium-high heat, stirring, until the sugar dissolves. Add the plums and vanilla bean and simmer until the plums are just tender, about 5 minutes. Transfer the plums to a plate using a slotted spoon, reserving the poaching liquid. Peel the plums, if desired, and slice into thin wedges.
Sprinkle the gelatin over 1/2 cup cold water in a small bowl. Let sit 1 minute, then stir into the warm poaching liquid until the gelatin dissolves. Pour through a fine-mesh sieve into a bowl. Let cool to room temperature.
Spray three 3-by-5-inch loaf pans or 8-ounce bowls with cooking spray, wiping out the excess. Pour a 1/4-inch layer of the gelatin mixture into each mold. Refrigerate until firm, about 20 minutes. Arrange half of the plum slices on top of the firm gelatin. Add just enough of the gelatin mixture to cover the fruit, then return to the refrigerator until firm, about 20 minutes. Repeat the process to make another gelatin layer and another fruit layer, then fill the molds with the remaining gelatin mixture and refrigerate until fully set, at least 3 hours or overnight.
Unmold the gelatin: Bring 2 inches of water to a simmer in a wide saucepan. Run a butter knife or small offset spatula around the top edge of the gelatin. Dip the bottom of each mold into the hot water for about 10 seconds, then invert onto plates.