Prepare grill to medium-high heat. Sprinkle fillets with 1/4 teaspoon salt and 1/4 teaspoon black pepper. Place on grill rack coated with cooking spray, and grill for 4 minutes on each side or until desired degree of doneness. Place tomatoes, onion, and jalapeño on grill rack coated with cooking spray; grill tomatoes, cut side down, 6 minutes. Turn; grill for 1 minute. Grill onion and jalapeño for 6 minutes on each side or until lightly browned. Remove from grill, and cool slightly. Coarsely chop tomatoes and onion; finely chop jalapeño. Combine tomatoes, onion, jalapeño, 1/4 teaspoon salt, 1/4 teaspoon black pepper, and juice from 1/2 lime. Serve salsa over fish. Garnish with lime wedges.