Hey Krazy. I'm gonna give you a little bit of a different take.
I don't have any experience with slender tone specifically, but I do have experience with the electrical impulse exercise systems.
It does indeed work to strengthen your abs, but it does NOT tone. You will gain strength in your abdominals without a doubt. But unless you diet correctly and lose the fat surrounding your abs, nothing will show from an aesthetic standpoint.
HOWEVER, from a strengthening standpoint, your core muscles will get a hell of a workout! You will (if you actually stick to the regiment) get much stronger in your midthoracic region. Bruce Lee used them quite a bit, and he swore by them. (of course, he had the metabolism and diet like no other.)
Another thing. It's not as easy as they advertise. While you don't actually go thru the motions of doing crunches and sit-ups, it's equally as tiring use the electro-impulse systems. But consider it another alternative to doing crunches.
It does have the definite advantage of not putting your body in positions that will damage joints and other musculoskeletal structures.
Take home message: It works, but only when accompanied by another diet and fat-burning exercise regimen.
