I assume that you are referring to vibrating platforms sometimes used for pilates. Supposedly they were developed for astronauts to prevent muscle atrophy, maintain bone density/strength and for toning while in a zero-G environment.
I've seen one of the pilates vibrating platforms in a friend's upscale health club. I've not tried it myself or have hear much feedback about it. My friend says she's not tried it either or paid much attention to it. After seeing this thread, I did a bit of research on these platforms. From limited reading on the subject, i get the sense that these platforms may very well provide some benefits but probably nowhere as much as the exaggerated claims made by platform manufacturers.