Inspired by that infamous iPhone-OS-on-Mac-Pro movie, I got an idea to use the iPhone Simulator files to run SpringBoard and co. on x86 processors. It is possible anyway, because if you treat the Simulator's SpringBoard.app with "lipo" command-line tool, you'll get sth like this:
lipo -info /Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator2.0.sdk/System/ Library/CoreServices/SpringBoard.app/SpringBoard Architectures in the fat file: /Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator2.0.sdk/System/ Library/CoreServices/SpringBoard.app/SpringBoard are: ppc7400 i386
So, I copied half of Mac OS onto a pendrive and replaced some of the files with iPhone Sim's counterparts and booted it from EFI shell on iMac with boot.efi -s option.
Now, when I try to launch the SpringBoard, it crashes because there is no "PurpleEventPort" or sth like that (i'll post the log later), and seems there are some problems with graphics, too. If I launch /Applications/Preferences.app/Preferences -RegisterForSystemEvents, it runs but shows nothing and console is still visible. Anyone's willing to help with it? Currently I know that iPhone Simulator.app runs some sort of server on startup and if SpringBoard is launched and doesn't detect this server, it crashes.