1. Combine cider and sugar in a small saucepan over medium-high heat. Bring to a boil; cook until reduced to 1/4 cup (about 9 minutes). Remove from heat.
2. Cook bacon in a small nonstick skillet over medium-high heat until crisp. Remove bacon from pan, reserving 1 teaspoon drippings in pan; set bacon aside. Add chopped shallots to drippings in pan; sauté 1 minute. Remove pan from heat; stir in cider mixture, cider vinegar, 1/4 teaspoon salt, and black pepper.
3. Crumble reserved bacon. Combine bacon, Granny Smith apple, onion, and spinach in a large bowl.
4. Combine remaining 1/2 teaspoon salt, curry powder, and red pepper in a small bowl. Sprinkle salt mixture evenly over both sides of scallops. Heat oil in a large nonstick skillet over medium-high heat. Add scallops to pan; cook 3 minutes on each side or until done.
5. Drizzle cider mixture over spinach mixture; toss gently to coat. Place about 2 1/2 cups salad mixture on each of 4 plates; top each serving with 5 scallops.