For the blueberry sauce: In a saucepan over medium heat, combine the blueberries, 1/4 cup of water, orange juice, and Splenda. Stir gently, and bring to a boil.
In a cup or small bowl, mix together the cornstarch and 1/4 cup cold water. Gently stir the cornstarch mixture into the blueberries. I like to mash half of the blueberries and leave half of them whole. It's personal preference whether you want to mash the blueberries or leave them whole. Simmer gently until thick enough to coat the back of a metal spoon, 3 to 4 minutes.
Remove from heat and stir in the vanilla extract. Thin sauce with water if it is too thick for your liking.
For banana pancakes: Combine flours, one tablespoon Splenda, baking powder and salt. In a separate bowl, mix together milk, club soda, vegetable oil and mashed bananas. Stir flour mixture into banana mixture just until all is moistened.
Whip egg whites with 1 tablespoon Splenda until stiff peaks form. Gently fold the egg whites into the pancake mixture.
Heat a lightly oiled griddle or frying pan over medium heat. Pour batter onto the griddle, using approximately 1/4 cup of batter for each pancake. Cook until lightly browned on the bottom, 3 to 5 minutes, then turn and cook until the second side is brown. Serve hot with the blueberry sauce.