Never ever get me on one of those things. Read that waiver carefully, especially the small print, and especially the part about cancer.
http://www.t-zonevibration.com/faq
While T-Zone Vibration is very safe, there are some people who should not use vibration. If you:
Have active cancer
Have an active herniated disc
Have a pacemaker or other implants
Have had recent surgery
Have serious cardiac disease
Or if you are pregnant (or think you might be)
This list is not exhaustive and if you have any health conditions whatsoever, please discuss with your local studio along with your health care provider.