The Chi Machine is a device that looks like a small suitcase with two ankle rests on the top. You lie down on the floor, on your back, and place your ankles on the rests. Then, you turn on the machine and for about 15 minutes it shakes your legs. I've tried it and can tell you that the experience is fun, feels good, and produces a rush of energy up your legs when the motion stops. Whether Chi Machines live up to the many and varied health claims made for them is another story.
I can see where using a Chi Machine is relaxing and therefore might help with such stress and tension-related symptoms as backache and tension headaches, but there's no scientific proof that it will.
I would be even more dubious of the other claims. The manufacturer of the Chi Machine also calls it an "oxygenating massager" capable of increasing oxygen in the body, "pumping" the lymph system, aligning the spine and delivering the benefits of walking 90 minutes in a 15 minute treatment during which you do nothing but lie there while the machine jiggles your legs.
Even less plausible are claims that it improves the function of the Internal organs, strengthens the immune system so that you get few or no colds, improves your circulation, firms and tones your thighs, hips, buttocks, stomach and breasts, improves skin tone, and alleviates menstrual pain, arthritis, constipation, and asthma. To my knowledge there have been no scientific studies that either validate (or disprove) any of these claims.
However, I would recommend learning a relaxation technique such as deep breathing, yoga or visualization, all of which can help with tension headaches. You could also try Shiatsu massage or Trager work. Osteopathic manipulation from a doctor trained in craniosacral technique can help with headaches stemming from musculoskeletal problems in the upper back and neck.
Andrew Weil, M.D.