touchHLE is a high-level emulator for iPhone OS apps. It runs on modern desktop operating systems and Android, and is written in Rust.
touchHLE's high-level emulation (HLE) approach differs from low-level emulation (LLE) in that it does not directly simulate the iPhone/iPod touch hardware. Instead of running iPhone OS inside emulation, touchHLE itself takes the place of iPhone OS and provides its own implementations of the system frameworks (Foundation, UIKit, OpenGL ES, OpenAL, etc). The only code the emulated CPU executes is the app binary and a handful of libraries.
The goal of this project is to run games from the early days of iOS:
Currently: iPhone and iPod touch apps for iPhone OS 2.x and iPhone OS 3.0. (iPhone OS 3.0 support is a recent addition and is not in a release yet.)
Longer term: iPhone OS 3.1, iPad apps (iPhone OS 3.2), iOS 4.x, …
Never: 64-bit iOS.