The iPhone and iPod touch port of Kenta Cho's rRootage is now available from the App Store, courtesy of Lazrhog. All modes from the original are included, although one major drawback is that the game has no sound effects.

rRootage Shooter Now Available for Free (Touch Arcade)
Kenta Cho's rRootage Hits iPhone (Wired)
Noiz2sa iPhone Port (IndieGames)