A colleague of mine gave these machines a try. They came with instructions in English and described the different ways you body would be 'violated' - i kid you not, this was the word used! 

You mean those little blue things with a few moving mechanical parts? Yeah, I've tried them. They can actually be really fun. I like the ski versions; they're basic, ghetto, yet totally fun. I go in-place skiing on them.

They ARE useful if you want to lose weight by doing repetitive motions and such. It's good to keep you in shape, even if they aren't as advanced as the ones back home.

a few years back there was this foreigner here who would just get plastered every night.  one night in particular has stuck in my memory.  he had a beer or 12 too many and decided it would be a good idea to play on those "things" for a lack of a better word.  there's a thing that replicates the motion of swiveling your feet in a circular motion while your upper body remains facing forward.  i'm not sure how this happened, but he ended up face planting it into the center metal pole.  blood was gushing from his nose and mouth.  after about five minutes of historical laughing, we decided to buy him a beer to make the pain go away.  the next day, he called us asking who he had fought the night before. 

I think some of them are good, and the "skii version" where you are standing still swinging your legs back and forth it probably good for older people as it is no-impact, and you can work up a sweat. 

In our community we have playgrounds with swings, slides etc for children to play, and their grandparents are often using these fitness machines. There are at least 6 different types of exercises. The one I like most is one that exercises the pecs. Using it feels exactly like the machines in a gym, but this one is using your own body weight as resistance, meaning a fat bastard like me can get a good workout. 

The things are used a lot. For me there is more purpose in swimming, running or just walking the dog. I need to move so I can feel my heartbeat go up otherwise I find it pointless. 

We have 3 of them on the terrace opposite to my office. 1 is actually just a frame with rolls to massage your back, one is the pecs Scando mentioned and the 3rd, my favorite, is the skiing one (but this one swindles left to right). I like it. Everytime I take a break and I go outside, I play with it 2-3 minutes, enough to make me feel dizzy and unable to walk a straight line back to the room.

These outdoor "gyms" are everywhere in China and I've seen oldies, teens and toddlers using them. They're fun, practical, and they provide some form of mechanical exercise that you would ordinarily have to go to a gym to perform.

I think they are a great public service and a few Western countries (most notably, the U.S. where obesity is endemic) would do well in adopting similar public "playgrounds" in neighborhoods round the country. They are free, weather-resistant, and they provide people who can't afford to go to a Gold's Gym, Planet or L.A. Fitness an opportunity to stay in shape.

I would export them to the West in a heartbeat if I knew how to do it. All it takes, I would imagine, is convincing "City Hall" in Smalltown, U.S.A. or elsewhere that the public good would benefit. And the benefits would outweigh the costs, ultimately.