Since my back has been owwie Mother bought a massaging plus heat computer chair.  Oh my yes, good times.  Now I can’t think of any viable reason why you have the option of it vibrating on the seat in one very particular location.  In fact, when Mother went to buy the chair the cute sales guy asked her, “Now tell me, why’d you pick that one?”  She went into a spiel about a daughter with a bad back.  But hey!  This is just a fun bonus.