Chi-gung is a really good exercise. While it is part of Tai-chi, some of the styles of chi-gung (called, "animal exercises" or "Zookinesis") are more vigorous and combine Chinese Yoga and the warm-ups of animal styles of kung-fu. There are some zookinesis exercise videos on the youtube channel, zookinesis49.
The one called "Zookinesis: Chi-gung for Fitness" is a great combination of exercise and stretching. There is a seated one: "Zookinesis: Chair Exercises for Weight Reduction".