The 5MX keyboard is fabulous, it is the best I have ever used in a PDA device. And the power requirements of the thing are something to be envied today, it runs on 2 AA batteries for weeks in normal usage!

Granted, it only has greyscale display but it does run X11 on it fairly well.

The usability of 5MX as a communications device is slightly limited by the fact that there's no network interface, you can of course run SLIP over the RS232 interface but the 9600BPS limitation makes it a perfect piece to practice the virtue of patience on.