[Update: April FoolsGmail Motion doesn’t actually exist. its merely an April Fools prank from Google]

Gmail Motion - How it works

How it works

Gmail Motion uses your computer’s built-in webcam and Google’s patented spatial tracking technology to detect your movements and translate them into meaningful characters and commands. Movements are designed to be simple and intuitive for people of all skill levels.
Gmail Motion - Motion Guide

Motion Guide

Familiarize yourself with some of the basic functionality of Gmail Motion using this printable guide of sample gestures. With it, you’ll be able to start writing and responding to emails