If you look back at Apple’s Newton PDA device, it’s pretty clear that it was a major inspiration for iOS. You could say that Newton was the iPhone’s grandfather. Now, through the Open Einstein project, iPhone users can run an emulation of the Newton OS right on their modern devices.
Downloading the code from the Open Einstein project’s site allows you to experience touch technology in its infancy, right from the comfort of your iPhone, iPod Touch or iPad. You can also run the Newton OS using Mac OS X, Linux (with X11), Windows and several ARM-Linux PDAs.