The modification of the Game Gear is known as the “Handy Gear.” It adds a 5″ screen, internal rechargeable batteries, new casing, and master gear converter hardwired on! The Ben Heck forum user wanted to keep the game gear looking like its old self as much as possible. Check out these build screens: here.
Total win! Hopefully SEGA will release some of the stranger Game Gear titles (including Panzer Dragoon Mini on the 3DS) because otherwise I want this thing!
[Source: Ben Heck]