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 v1.3.2:

[nervegas] Added HSyncs for overclocked situations (DMA, etc)
[nervegas] Added 512 clocks for DMA writes
[nervegas] Fixed vblank flag (set @ 240), rolling thunder levels fix
[nervegas] Fixed vblank end = scanline 261 (0-indexed)
[nervegas]Added support for player 2 controller (touch top gray bar)
[jordan] Added 8-step CPU cycle between IRQ and NMI
[jordan] Moved CPU step to before sprite hit, fixed minor rendering
[nervegas] Added “mid-button hot spot” allowing both A/B to be pressed by rolling the thumb from one button to the middle of both.

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