The latest exercise my son's developmental optometrist has recommended for our whole family is to use a rebounder.
This is "rebounding Edna," by the way.
I've tried our neighbors' rebounder, and it really is fun and comfortable. This link lists some of the health benefits supposedly derived from rebounding including stimulating the lymphatic system, improving muscle-to-fat ratio, better oxygen circulation, improved resting metabolic rate and several others.
Actually, Edna does not have it quite the way Dr. Sobek instructed us to use it. He said the key is that one's feet should not leave the surface, but rather the legs should pump one up and down on it.
I freely admit that I hate to exercise in non-functional ways. I mean, I don't mind stretching while I scrub the floor, or running up the stairs an extra 10 times to get something, or walking to enjoy being outside, but the thought of doing exercise just because it's exercise is very difficult for me to accept. But I could see myself rebounding just for the fun of it. I'm still hunting for one to buy that still allows me to keep both arms and both legs. Which really isn't all that hard, but I also don't enjoy shopping. What I do is far more like deer hunting: find it, bag it, bring it home. Or better yet, buy it on line and have it delivered!