I have one!
They are pretty cool! The eMates have an Apple serial connector and the newer style Newton 2000 style ports. They have a rechargable battery and a nice bright backlight display and a built-in keyboard. They are pretty quick and cool to play with. Tthe keyboards and serial adapters for the Newton 2000s are rare and expensive, so an eMate is a good solution, plus it gives you the power for a Newton 2000 without the hassle of expensive cables and adapters.
I have a Newton Fax Modem, Newton 130, Newton 2000, and an eMate 300 😎