Far Infrared?
I have tried a "chi machine" - it was interesting.
First off, it has absolutely NOTHING to do with the TCM concept of chi. So, if that's what you are looking for, it is complete snake oil.
In practice, the client lays supine with their heels/ankles resting on the top of the chi machine. The feet are close together and the legs are somewhat elevated. When activated, the chi machine begins to move the client's ankles from side to side. It's a fairly smooth action with a limited ROM. The rhythmic side-to-side motion provides a gentle "whipping" undulation of the legs, hips, and torso. It is an extremely odd sensation, but I didn't find it terribly uncomfortable. (Then again, I am comfortable with neck cranks, being choked, having my joints locked, being thrown onto hard surfaces, hit in the face, kicked in the groin, etc.... so my perspective may be skewed.)
After a minute or so, I was feeling oddly "rubbery" - but not in a particularly good or bad way. The therapist then switched off the machine, stating that she never lets first-timers start with more than a minute, as many people feel extremely ill and a few have had to throw up. However, she said, over time people develop a greater tolerance and can spend much more time. The only people she uses it with are those with impaired lymphatic flow, and she stated that it can be helpful in reducing edema if not too progressed. However, she usually starts with manual lymphatic drainage to make sure the client will be able to handle the machine before introducing it into the treatment process.
I'm not eager to retry the experiment, but it was interesting.