Developer Matt Gemmell recently wrote a fun post in his blog about connecting a Newton eMate 300 to a modern Mac. The setup required the use of a serial cable and a serial-to-USB adapter as well as the Newton Connection for Mac OS X software. Gemmell describes the process in detail.
In addition, Gemmell offers some excellent advice about orphaned software: get it while it's available and don't assume that you can find it in the cloud on some future date.
Firstly, as with any retro technology, if you have a Newton and think you’ll ever want to connect it to your modern Mac, I’d advise you to download the relevant software and drivers right now, while they’re still available. It’s probably also a good time to obtain the necessary cable and adapter. If you wait a few years, it’ll probably become a lot more difficult.
He points out that the Einstein Project lets developers run the NewtonOS in emulation on various platforms including iPhones, iPads and Macs.
Of course, anyone can run it if they want to, but they will have to jailbreak their devices to do it, since the emulator requires users to upload a Newton ROM image. (Neither Apple or I approve of jailbreaking.) This is one reason that it was rejected by the iTunes Store — another being that Apple likely didn't want a whole OS and app platform running on iOS devices, even as a curiosity and even if it came from Apple.
I liked this bit about launching Einstein on an iPhone or iPad.
When you launch iEinstein with ROM installed for the first time, it will need to set up the entire Newton system. It will take up to a minute until the Newton logo shows and another minute until you are finally asked to input some personal information.
Don't bother setting the date: NewtonOS has a bug and can not support dates after January 2010. There is a patch available which may or may not work with the emulator.
Eventually, Notes will show icon bar at the bottom of the screen and you can write text, and run other packages available online. Neat! This is almost something that might make me want to jailbreak my iPad. Maybe when I graduate up to the new iPad, I will make my old iPad a Newton. A useful reuse and upcycling of older hardware and software.