On OS X though, https://pqrs.org/osx/karabiner/ will, among many other features, share the state of modifier keys between keyboards. That way you don't need to get out the hack saw.
I'm not sure how much keeping your wrists straight helps with RSI. When people thought it carpel tunnel syndrome the idea was to keep your wrists straight. The real problem seems to be the cheap rubber dome or scissor switches that only activate when you bottom out the keys.
I did a radical switch to an Alphagrip keyboard, which is still membrane switches (as far as I can tell). No more random twinges of pain. The primary difference is that I no longer wrest my wrists on anything (even a gel type pad), but it could also be that I don't use as much force to activate the keys when my fingers are already there.
Yep, that's the one! I can get around ~60wpm (100wpm on a qwerty keyboard) with normal text and passable at programming. Took about a month of daily typing lessons to get that fast and I still need a regular keyboard around for annoying key combos.
In my case switching from a regular mechanical to a Microsoft Natural Ergonomic 4000 at home and work completely relieved all the issues I was having with wrists and forearm pain.
Easily the best 100 quid I ever spent (for the pair).
A more expensive but less error prone and a better looking solution would be extending the link between this split keyboard http://www.amazon.com/Kinesis-Freestyle-Solo-Ergonomic-Keybo...
I am frustrated with mine that I can't place the halves wider and was considering something similar.
The Matias Ergo Pro uses a standard TRRS connector between its two halves. You can buy essentially any length on <insert your favorite commodity cable dealer here>.
There's currently an Indiegogo campaign going on for pre-assembled Ergodoxes [1]. I'm not really comfortable with early-stage hardware crowdfunding, so I'll still be sourcing and building my own.
This guy is a bit much between the hair, the kneeling chair, and the custom keyboard. And yet the world is undoubtedly better off for having people like him around, tinkering.
On OS X though, https://pqrs.org/osx/karabiner/ will, among many other features, share the state of modifier keys between keyboards. That way you don't need to get out the hack saw.