I've been looking into Scientology, and the E-Meter that plays a large part in the rituals. Isn't the e-meter simply a lie detector? It certainly seems to measure the same things as one.
The simple answer is "No. The e-meter is not a lie detector."
A lie detector is a very complex device that measures many different physical reactions. The e-meter measures only one thing: electrical variations caused by changes in a person's spiritual state. It does not detect lies, it detects spiritual changes. When the e-meter reacts you don't say "Oooh, you lied!", you find out what caused it to react. There is no "lie" reaction.
The specific reactions that occur on the e-meter have been carefully documented. There are 28 reactions and each indicates a specific spiritual state or change of state.
The e-meter is used as part of Scientology Auditing to help locate areas of spiritual distress or travail so they can be addressed and resolved.
From personal experience both as an auditor and as a preclear, I can tell you that the e-meter is extremely accurate and indispensable when helping another being locate the areas of their lives that need attention.
Here is more data for you: The E-Meter
I hope that answers your question.