In a small saucepan, combine sugar and gelatin. Stir in nectar. Cook and stir until sugar and gelatin dissolve. Remove from heat.
Meanwhile, in a blender container or food processor bowl, combine peach or apricot chunks, yogurt, and vanilla. Cover; blend until smooth.
Pour fruit mixture into a small bowl. Stir in gelatin mixture. Cover and freeze for 2 to 3 hours or until almost firm. Beat with an electric mixer on medium speed about 2 minutes or until mixture is fluffy.
Transfer mixture to an 8x8x2-inch pan. Cover and freeze for at least 4 hours or until firm. (Or, freeze gelatin mixture in a 2-quart ice cream freezer according to manufacturer's directions.)
To serve, let stand for 10 minutes at room temperature. Scrape or scoop into dessert dishes. Makes 6 servings.