I am no expert on such things, but from my understanding there is no electricity flowing in the body. At the wrists I think there is just a tiny "induced" current caused by the pulse which I believe is only in the blood directly below the electrodes, not in the whole body. Because the blood apparently flows 12 times an hour through that spot eventually all the blood would be subjected to a tiny current at those two points in the arteries.
So there is no actual current being applied to the body, just an induced current immediately below the electrodes.
Same sort of thing with the magnetic pulser which induces a tiny current only in the path of the pulser paddle. No current is actually being applied to the body from the pulser.
Hope it helps and I hope I get corrected if I am wrong.