QEMU-iOS is an emulator for legacy Apple devices. Currently, the iPod Touch 1G and iPod Touch 2G are supported.
The schematic below shows the most important hardware components of the iPod Touch 2G and their interactions. The schematic for the iPod Touch 1G is mostly similar.
Instructions on how to run the iPod Touch 1G emulator can be found here. A technical blog post with more information about the peripherals and reverse engineering process is published here.
Instructions on how to run the iPod Touch 2G emulator can be found here.