I got this from the website
http://atlantamartialarts.com/articles/stretching/index.html
"Split-Stretching Machines"
"Many of you may have seen an advertisement for a split-stretching machine in your favorite exercise/athletic magazine. These machines look like "benches with wings". They have a padded section upon which to sit, and two padded sections in which to place your legs (the machine should ensure that no pressure is applied upon the knees). The machine functions by allowing you to gradually increase the "stretch" in your adductors (inner-thigh muscles) through manual adjustments which increase the degree of the angle between the legs. Such machines usually carry a hefty price tag, often in excess of $100 (American currency).
"A common question people ask about these machines is "are they worth the price?". The answer to that question is entirely subjective. Although the machine can certainly be of valuable assistance in helping you achieve the goal of performing a side-split, it is not necessarily any better (or safer) than using a partner while you stretch. The main advantage that these machines have over using a partner is that they give you (not your partner) control of the intensity of the stretch. The amount of control provided depends on the individual machine.
"One problem with these "split-stretchers" is that there is a common tendency to use them to "force" a split (which can often result in injury) and/or to hold the "split" position for far longer periods of time than is advisable.
"The most effective use of a split-stretching machine is to use it as your "partner" to provide resistance for PNF stretches for the groin and inner thigh areas (see section PNF Stretching). When used properly, "split-stretchers" can provide one of the best ways to stretch your groin and inner-thighs without the use of a partner.
"However, they do cost quite a bit of money and they don't necessarily give you a better stretch than a partner could. If you don't want to "cough-up" the money for one of these machines, I recommend that you either use a partner and/or perform the lying `V' stretch described later on in this document (see section Working Toward the Splits)."
Kind of good to know, if you're considering the investment. Hope this helps some of you.