Heat oven to 350 degrees F. Line a large baking sheet with nonstick aluminum foil.
Place the 1-1/4 cups of pecan halves and 1/4 cup of the Splenda in the work bowl of a food processor. Process until pecans are finely ground. Set aside.
Place egg whites in a clean large bowl. Add salt and beat on medium-high speed until soft peaks form. Add remaining 1/2 cup Splenda, one tablespoon at a time, while beating. Add vanilla extract and continue to beat until stiff glossy peaks form. Gently fold in the ground nut mixture.
Dollop mixture onto prepared baking sheet to form 24 cookies (about 1 rounded tablespoon each). Place a pecan half on top of each cookie.
Bake at 350 degrees F for 15 minutes. Remove cookies to a cooling rack and allow to cool completely. Makes 24 meringues.