Yip, I remembered checking that one out some time back, no proof that it actually works, just slanky scheister salesmen.
I remember someone trying this product when going on holiday one year long ago, that was on a 3.0 cortina bakkie (pick-up truck), it caused their vehicle to stall several times on their way, needless to say, the device ended in the trash can.
Oh, and if you should come across it in the future, similar thing: using magnetic fields to soften hard water, that one is also a no-go theory.
But magnets are really decent to keep your take away price list on the fridge.