Combine in a small bowl curry powder, cumin, salt, and pepper. Set aside. Remove excess fat from meat. Cut meat into 1-inch pieces. Sprinkle spice mixture over meat. Place meat in a 4 1/2- to 6-quart slow cooker. Add undrained tomatoes, celeriac, cauliflower, onion, and apple.
Cover and cook on low-heat setting for 9 to 10 hours or on high-heat setting for 4 1/2 to 5 hours. Turn off the cooker. Stir in coconut milk and peas. Cover and let stand for 5 to 10 minutes or until heated through.
In the meantime, combine in a small bowl the yogurt, cucumber, and lime juice. Top each serving with a dollop of yogurt mixture.