Leading on from the electro-magnet therapy stuff, we have this:
1) Get a small basin (but large enough to put both feet in).2) Add some water and enough salt to make it taste salty, not so much water that if you put your feet in, it overflows.
3) Get a car battery, some wire, and a couple of iron nails (prolly a switch, too).4) Wire the battery from each terminal to a nail, with the switch in the circuit so you can cut the volts. Put each nail in the basin, but well separated (obvs).
5) Invite the mark to put his feet in and turn on the volts.6) Tell the mark that this is a device to draw the toxins out of his body via the feet. Point out that as the water becomes discoloured, that's the toxins coming out, that there's a fresh, sea-side like odour (that's the purification process), and that his skin starts to feel soft and soap like as a further result of the purification process.
7) See how much you can take off the mark and repeat until rich. Perhaps see if you can sell the process to Gwyneth Paltrow.8) Make sure the mark doesn't notice that all the above effects will occur even if he puts NO part of his torso into the basin.