Instructables user Mikamika explains in a three-post series that you build the jacket with neoprene, two layers of conductive fabric, and perforated foam to build in the separation between the two conductive layers until pressed. You can also check the GeekSugar link or Instructable for videos of the jacket in action.
After watching the video, we're not sure how relaxing this would be, but if you have knots, the repetitive pressing of the "buttons" might help the situation. In any case, this is a definitely creative project!
- Image from GeekSugar.