1. Bring water to boil in medium saucepan over medium-high heat. Add cranberries and sugar substitute. Cook and stir until mixture returns to boil. Reduce heat to medium and simmer, stirring occasionally, 10 minutes, or until cranberries have popped open. Mixture will be thickened.
2. Pour gelatin into medium heat-safe bowl. Pour hot cranberry mixture over gelatin and stir until gelatin dissolves completely.
3. Stir in cold water, orange peel, diced orange, and celery. Mix well and pour into an 8-inch square pan and refrigerate until set, about 4 hours.