Pipe Wire

In BuildCraft, there are 4 types of Pipe Wire: Red, Yellow, Blue, and Green. These are placed on a Transport Pipe, Kinesis Pipe, or a Cobblestone Structure Pipe. These can be used to interact with Gates.

Usage
When pipe wire is placed on a pipe, gates on the same pipe can be set to output a pipe wire signal when a certain condition is true. Then, a gate on the another pipe can detect if a pipe signal is on and output a redstone signal. This in essence allows a player to have redstone signals travel down pipes.