It's not just Ctrl-[ that does this, Escape does it too. We just typically don't toggle between insert mode / ESC in vim fast enough and enough times to notice it. With the pedal it's quite easy to press and release it a bunch of times before you type anything.
I have found the Cherry MX switches to be fairly good and reasonably priced.
I did some research to see if anyone had open sourced a design for a 3D printer to print a Spiffchorder, but I didn't find anything. Maybe that's the next step? 3D printing these iteratively, to see what fits and what needs to change, seems like a huge win for developing a wearable chording keyboard that is comfortable and durable.
This is in the works. While it won't be three pedals to start, I realized the simplicity of wiring the Teensy to a digital piano foot pedal (like this: http://www.amazon.com/M-Audio-Sustain-Pedal-Action-Keyboards...) to build a relatively cheap, durable foot pedal for computing. I'll be posting about that sub-project soon on my blog.
One thought, since the Teensy can detect button press and button release events, is to code a vim mode where holding the pedal puts you in insert mode and releasing the pedal hits ESC to leave insert mode. We'll see how that works out in practice.
For 3 pedals, you could go with a DIY guitar pedal solution of project boxes and 3 momentary stomp switches (http://www.mammothelectronics.com/ is a good supplier of these parts) but I am unsure about the ergonomics of using one of these pedals constantly. (Guitarists simply stomp them on and off from a standing position. They're generally not pressing and holding the switches for 8 hours from a chair. So it might just cause foot/ankle problems due to the height of the front of the enclosure. More experimentation is needed on my part in this area.) Such a pedal would be way cheaper than the commercial versions from Kinesis and other manufacturers, however, and should be far more configurable / useful on Linux & Mac.
I'm really looking forward to getting a Leap Motion device! I think there's a lot of possibility there for programmers that are interested in building a new input method.
My thinking is that a Leap Motion could be used with a standing desk (my current preferred desk setup), in combination with existing keyboard and mouse, to replace key combos to the OS like switching windows/tabs, window management (maximize, minimize, expand to left half of screen, etc.) as well as macros for common commands we type all day (`git push` or running the tests, for example.)
The section "The NLS System: Engelbart and English" contains the most detailed explanation of Engelbart's chording keyboard that I've found, and the rest of the chapter is an interesting read.
I'm liking it a lot, as well. We'll see if my other team members want to use it tomorrow at the office. We actually use an intranet tool that we build for clients for project management at work, but I'm not convinced that it manages a software development project well.