Powder gingersnaps in a food processor or blender.
Set aside.
Combine gelatin, sugar replacement, and water in a small saucepan or microwave-safe bowl.
Stir to mix.
Heat until gelatin is completely dissolved.
Remove from heat.
Meanwhile, mash two of the bananas.
Stir the 3 tsp (45 mL) of lemon juice and the lemon peel into the mashed bananas.
Stir banana mixture into gelatin; then allow to cool until mixture is the consistency of thick cream.
Add egg whites.
Beat with a rotary beater until mixture begins to hold its shape.
Chill if necessary.
Spoon mixture into the baked pie shell.
Chill thoroughly.
At serving time, slice remaining banana and dip each slice in lemon juice.
Garnish top of pie with banana slices; then sprinkle with powdered gingersnaps.