NES.app is a Nintendo emulator for Apple’s iPhone. NES.app uses a modified version of the popular InfoNES emulation core to mimic the 6502 processor in a Nintendo Entertainment System, allowing you to play ROM dumps of games designed for the NES console. ROM dumps are files containing the dumped instruction code from a physical cartridge. In many cases, you are legally entitled to posess a ROM dump of any game that you presently own. ROM images for NES are widely available online, or with the appropriate hardware, you can dump them yourself directly from the cartridge.

NES.app started as a fork of iPhoneNES v0.01, but has been completely rewritten to run very fast, and with many additional features including full sound, game genie codes, saved games, battery-saved ram support, and full screen support.

Changes since v1.3.1:

Allow A & B to be simultaneously pressed. NOTE: Only two buttons can be pressed at a time per Apple
Rewrote save state / wiring routines for better compatibility
Added mapper state hooks for seamless mapper state save NOTE: Saved games from prior versions are incompatible
When auto-frameskip, set default skip to 1 when restoring
Suspend emulator when changing orientation to avoid crashing
Fixed Game Genie code entry

http://iphone.natetrue.com/nesapp/