Shinobi Gauntlet

The is a  developed by Katasuke of Konohagakure's Science Ninja Weapons Team.

Overview
As its name suggest, this tool is worn on the forearm. The user can put a small scroll into it and unleash the technique that was sealed into the scroll beforehand. Because this requires no skill, it is possible for anyone to use any kind of technique regardless of its rank or restrictions.

Trivia

 * Masashi Kishimoto thought of a tool like this since before Naruto began. However, he could never introduce it into the manga.