Pax,
That's an electrical muscle stimulation system. Bascially, you put those belts, arm wraps etc. around the targeted area with electrodes and gel pads on the skin, by delivering electricity through the muscles, you stimulate muscles contraction. You can see and feel your muscles contracting. So in short, you are exercising without having to lift a finger. The slendertone system is different from other similar systems in that it can deliver higher power electricity, so that the muscles really contract instead of you just zapping yourself for accupunture or massage. I know it really works because 1) I got muscle cramps as if I had really worked out 2) My tummy got smaller 3) I felt hungry after using the system like I used to feel hungry after a workout
Having said that, you still need to use it at least twice a day, not just once as stated. You also need really high power for it to show effects. I can't go very high on my arms cuz can't tahan the tingling. At most, go up to 60 at my arms but I can go all the way to 99 on my tummy! After you took off the belts, you can really feel that the area around is warm and "exercised". It really can burn off calories too. It worked for hb too but he is so lazy he can't even be bothered to workout "sitting down".