In a Dutch oven or kettle, combine rhubarb, sugar, and water. Bring to boiling. Boil rhubarb, uncovered, for 3 minutes, stirring constantly.
Stir in blueberry pie filling. Return the mixture to boiling; boil for 6 minutes, stirring constantly.
Stir in gelatin. Return to boiling; boil for 3 minutes, stirring constantly.
Ladle into half-pint jars or freezer containers, leaving 1/2-inch headspace. Seal and label. Let stand at room temperature about 8 hours or until jam is set. Makes 8 half-pints.
Prepare the jam as directed. Store in the refrigerator for up to 3 weeks or in the freezer for up to 1 year.