Nice project. I have to admit though, this must be the last last resort after all last resorts. Using a phone input for real work is going to be frustrating, especially for keyboard.
I think I would rather use the phone camera faced on a paper printout of a keyboard, viewing my finger movements and inputting that instead.
I suggest using Unified Remote to connect PC with Android phone.
I hacked something like this a few months ago. Mine works on Mac OS X too; wonder why this one doesn’t (at least it is not in the list; I did not test yet).
I really needed something like this last year when I didn't have any wired keyboards laying around.
I was thinking about needing something like this a couple of months ago. But just as a mousepad.