I used an external USB keyboard but it was messy to get working as it had a UK Layout and needed a special driver to map the keys properly.
I then got a Neewer Ultrathin 2.4G 2.4GHz Wireless Keyboard Mouse For PC Laptop which meant that I have both keyboard and mouse on one USB Port. The layout of the keyboard is the US one and everything seems to map properly - I really needed the pipe (|) symbol for use with a Terminal Emulator and this combo worked fine without any special driver.
The keyboard is a generic Chinese import (all instructions in that language) and other similar ones may be the same.
This looks like a useful approach for anyone who wants to do a bit of hacking without relying on a host PC and ADB connection. I suspect that the wireless approach with the keyboard/mouse powered by AAA cells will suck less power from the tablet than a direct USB connected device.
BobC