The E-meter is a quack device used by Scientologists in a religious ritual called "auditing" in which changes in skin potential are said to indicate past traumas (including traumas from past lives) being re-experienced and cleared from your psyche.
After extensive litigation, Scientology started adding a disclaimer to its E-meter packaging and manuals saying that "by itself [the E-meter] does nothing."
Early E-meters were crude electronic devices, often compared to soup-cans by Scientology critics. But the modern models — which cost $5000 — are extraordinarily well-engineered as Play With Junk discovered when he bought a 2006 model on Ebay (for $100!) and did a teardown of it for his YouTube channel.
What's most impressive is the quality of the components that go into a machine that effectively only measures the resistance of the human body. The 'trim' pot is a Vishay wire-wound precision potentiometer that costs somewhere between $20 and $60. The power switch is an over-specced switch that probably costs $5. The control pots look and feel great, and the wiring is wrapped around chokes.
What's Inside A Scientology E-Meter? [Brian Benchoff/Hackaday]