It's so fantastic that even very low frequencies such as 5 or 10hz (5 times a second doesn't even sound that tiring!) are proven to be effective! I think it's great to make "zapping" as simple and cheap for people as possible. Why overcomplicate something simple? :)
It seems that precise amount of power, precise technique and whether or not water are used are not essential, as long as you get about 7 minutes of pulsing electricity through the body?
EDIT -- Ok I've started the 7-20-7-20-7 method and will do it every day :) Tomorrow I'll pop down to Maplin (I think that's our equivalent of Radioshack!) and get... whatever you use to regulate a frequency in a circuit, so that I don't need to manually tap anymore! lol I know I could just buy a cheap zapper, but I quite like building it myself! ^_^ Incredible that it's all so simple!