No!! Don't do it. Absolute rubbish.
They are good if you just want to tone up a bit, and they are "apparently" good at reducing cellulite, but I do not believe they shift pounds - as the manufacturers claim.
Also, have you used one before? They're horrible! They shake your head around and, for me, gave me nothing but a horrible headache.
There are lots of reasons why you *shouldn't* use one so, if you do go ahead with it and get one (which I would advise against) then read up on that first.