Reminds me of the story in which the police were interrogating a known criminal at the police station. They used a photo copier as a "lie detector" - when the thug answered a question, they would hit the copy button and out would come a piece of paper with the words "He's lying" printed on it.
The thug was not too bright and actually believed the copier was a lie detecting machine. He eventually confessed.
When I was in third grade I "invented " a shock machine. It was a small cardboard carton, about 1x2x3 inches, that had two leads with ring terminals on the ends. IT was called the shock box, which was quite amazing since inside the two wires were simply tied in knots so that they would not pull out. But then result was just as effective as if it had been a powerful shocking device. Of course the school authorities didn't take to it very well, but when it was opened for examination they realized it was harmless. But the fact that something could be believed with absolutely nothing to back it up is still amazing.
When I was in High School back in the 60's I got a plastic box and mounted a 10 microamp meter on the front. Inside the box I had a 9-volt battery in series with the meter connected to two screws with their heads exposed on the bsck cover of the box. I printed an official-looking "Marijuana Detector" label and put it on the front. I could wet my fingers and then when I pressed against the screw heads I could make the meter go up and down. It was fun to walk down a row of lockers as if the device was "sniffing" for drugs. I had some upperclassmen sweating bullets.
My Dad was in charge of Security and Safety for a grocery store chain at the time. When he found out about the device he asked if he could take it to work. He came home that afternoon laughing. It seems that he had pulled the prank in one of the stores. When he got close to one of the lockers an employee approached him and asked if he could resign without any further questions being asked. I guess the device really did detect marijuana after all!
David - He moved away the summer before high school so I lost track of him. He was back in town very briefly a few years later with some stories about both breaking into the school computer and helping administer it where he had been living. But I have no idea after that.
When I was in jr. high school (8th grade), I also had an extremely gifted and talented friend who would bring little electronic gizmos to school. I remember flashers, beepers and a pill bottle set up to shock people. Kids in our boy scout troop called him "Mmmm Buzzz Click."
We'd be walking though the school hallway and he would stick out his hand with the shock bottle toward someone and say: "Here. Hold this." Anyone who complied, of course, got a nice little shock.
One day he was talking about an oscilloscope that he had made from an old TV. When I asked him how he knew how to do all of that, he said: "I don't know. I just know." To this day I find that a fascinating answer.
Sadly, brains weren't all that well respected in the little logger town I grew up in.