Metal plates conducting electricity, especially direct current, will cause one of the plates to leach out its metals into the water which is what causes the water discoloration. It is not from some magic ultra-fast siphoning of toxins out of your body. Electricity does cause your skin to be more absorbent to whatever it is exposed to, in this case the listed metals. "Iontopheresis" is the medical use of a small direct current to heighten the ionic drug delivery in and through tissues of the body. The ionic drugs penetrate the skin from the electrodes by the current of the same polarity measured in milliamperes (mA). The amount of electrical current is normally around .5mA for each square centimeter of electrode surface.  The systems of Iontopheresis have been approved and in use for more than 20 years.

stainless steel composition: chromium, nickel, manganese, carbon, molybdenum
http://www.contractorsunlimited.co.uk/toolbox/stainless-steel.shtml

Electrolysis
http://en.wikipedia.org/wiki/Electrolysis#Electrolysis_of_water

On the positive side, if you are low in the listed metals it could be that limited use of an ionic foot bath can help you absorb a useful amount of them. But be aware that continued use can cause you to absorb more than your body needs which can have a toxic effect.

But this device does no more to detox you than any saltwater foot bath.