I ended up buying four pieces of equipment to help deal with being temporarily one-handed: the Matias half keyboard, the X-keys foot pedal (cheaper than the Kinesis pedals, which got lukewarm reviews on Amazon), the Keyspan PR-US2 Presentation Remote, and the Pacific Outdoors 17-LC100 Folding Recliner.
The good: I'm very pleased with the recliner and modestly happy with the remote. I got the recliner to take naps in; the brace on my arm didn't really accomodate lying down. This $80 recliner compares well with zero gravity recliners costing over 10x as much. (I've used two of the expensive variety; a BackSaver and one whose brand I don't recall.) The only downside is you can either sit up, or recline fully; there is supposedly a way to adjust the recline angle, but it doesn't really work. Expensive zero gravity recliners can all reliably lock at any angle you like.
The remote mostly worked as a mouse substitute that I could use with my immobilized right hand, reducing the need to slow down my left hand even more by switching from keyboard to mouse and back. Unfortunately, the mouse control pad is not nearly as good as one of the IBM "pointing sticks;" it appears to have four control points, like an old Nintendo D-pad, which gives only 8 possible directions to move in. This and a poorly quantized pressure sensitivity sometimes made things frustrating. If I were to do this again I would try a handheld trackball instead, even though I could not find any wireless models.
The bad: the half keyboard did not help programming speed with one hand, and the foot pedal didn't improve things. I've returned both.
The half keyboard gives you the left hand side of the keyboard, which toggles to the right side when the space bar is held down. So "a" becomes ";", "f" becomes "j", snd so on. For alphabetical keys, I found that it was true that I did not have to re-learn to touch type; I did not have to look at the keyboard, although I did have to pause and think, "does this one require the space toggle or not." I got up to about 20 wpm before giving up, compared to 25 with one hand on a full keyboard. I think I could have easily doubled that to 40+ wpm with enough practice to eliminate that pause and recognize "runs" of letters that can be typed without releasing the space, like "you," without thinking. But that kind of investment wasn't worth it because of a serious flaw.
The half keyboard is really more like a "1/4 keyboard." It only gives you the alphabetical keys and a couple punctuation marks. No number keys with their !@#$ counterparts. No F keys. No arrow keys. On a mac, you can have cmd or control but not both.
To allow these keys to be typed, there is a "numeric toggle" key that switches to keypad mode, and two other modes that you access by hitting "shift shift" and "shift shift shift." Almost any line of code you might want to type is going to run into this. Typing  for instance is shift shift s numerictoggle b numerictoggle shift shift a. Even the symbol-averse Java will need parentheses for method calls, and yes, parens require mode switching too. (As do braces. Shudder!)
So I lost in the non-alphabetical and modifier access much more than I could see myself gaining on the pure alphabetical side.
Finally, the modifier keys were on the right hand side of the keyboard where they very difficult to combine with shift. I tried to ameliorate the modifier key problems with the X-Keys pedal, mapping the pedals to cmd/ctrl/option, but that didn't really work either. (The included ikeys software wouldn't work at all. At least ControllerMate worked in non-X applications, but since Wing is the only IDE that does locals completion well, using a non-X IDE temporarily was a non-starter. Locals completion is nice with two hands, but absolutely essential with one.) Note that this is more of an OS X issue than a problem with these pedals; apparently mapping pedals (x-keys or kinesis) to modifier keys works fine on windows.
So, the half-keyboard is not useful for programmers. If it (a) were wireless and (b) had a non-skid backing -- it slid all over the place because the back side was just smooth plastic -- I could see it being useful for heavy smartphone users. But it fails there too. Good luck with this one, Matias.
Postscript: I considered trying the Frogpad as well as the half keyboard, but with users reporting that they got "up to 20 wpm after 2 weeks," it didn't sound worth the trouble. So if I ever had to spend another three weeks one handed I am not sure what is left to try. Probably I would try to use ControllerMate (os x) or xmodmap (linux) to make make a "half keyboard" in software that didn't suck so much, as suggested by one of the commenters in my first post.