Hardware modder, Chris Downing, has finished his second attempt at a portable and fully functional Sega Genesis. Named the Geneboy Reloaded, Chris has taken the hardware from a Genesis 3, the d-pad from the GameCube, buttons from a third-party Genesis controller and added a 3.5 inch screen to make his portable contraption. All the parts are enclosed in a custom-made vacuum formed shell.
For a homebrew project the system looks pretty impressive and Chris is currently selling it for $225 with the profit going towards future creations of his. You can find more details and backstory on the Geneboy Reloaded here.