ZodTDD, the developer behind GpSPhone (a Nintendo Gameboy Advance emulator for the iPhone and iPod Touch), announced the development of an N64 emulator for the iPhone and iPod touch. Zodttd believes that the current generation iPhone and iPod touch have the graphic CPU horsepower necessary to run those games. "...I can't promise it will run games top notch just yet, as things are too early to say. There's hope though, with a 3D accelerated graphics plugin, as well as an ARM dynarec."
As iPhone Savior points out, the toughest challenge could be fitting the controls onto the screen in an unobtrusive yet usable way. That was my main complaint about Resident Evil for iPhone [iTunes link] -- my hand is often in the way of what I'm trying to see.
Note that this will require an jailbroken iPhone or iPod touch.
[Via iPhone Savior]
Apple iPhone 6
Apple iPod touch 5th-gen