In a small bowl, whisk together yogurt, olive oil, lemon juice, honey, curry powder and 1/2 tsp. salt. Cover and chill until ready to use.
In a large bowl, toss chicken, apple, mango, celery and onion until well mixed. Add reserved yogurt dressing and toss well. Season with salt and pepper. Serve right away with whole-grain crackers or on top of salad greens. Alternatively, cover and chill to take for lunch.