In a bowl, mix mayonnaise, yogurt, and seasoned salt.
Heat a non-stick skillet over medium.
Season the chicken with salt and pepper, then add to the hot skillet. Cook 5-6 minutes on each side until golden brown and no longer pink in the center. Remove from skillet and cut into bite-sized pieces.
Dice celery and apple into small pieces.
Add chicken, apple, and celery to the yogurt mixture and stir gently until evenly coated.
Toss lettuce with dressing, and cut apples into slices.
Cut a slit in the side of each pita bread to open and form a pocket. Fill each with an even amount of the chicken mixture.