The emeter in scientology works the same way, all it is is measuring the conductivity of your skin much like a crude lie detector machine.
Why are people so easily duped?
http://www.cs.cmu.edu/~dst/E-Meter/
You can just use a multimeter and squeeze the probes and measure resistance in ohms and get similar result. If you are keen you can make some short copper pipes for your hands and connect them to it.
Multimeter can be had for £10.
Emeter = £1000s
Rayonex PS1000 = £1000s
And of course you will NEED special very expensive 'training' to be able to use the quack devices. Things that make you go hmmm.
The guy who was jailed for fraud selling fake bomb detectors was doing exactly this kind of thing, selling worthless cheap gimmicky golf ball detectors that are just fancy dowsing rods that have no working parts and repackaging them into very expensive and sophisticated bomb detectors and convincing the hapless and desperate that they worked.
If I told you that your £10 multimeter could detect illness and cancer let alone say it can cure it you would think i was nuts, if I told you your £10 multimeter can detect alien ghosts you should also think I was nuts. If I sold them for £1000s then you should consider me a fraudster.