I bought this
Show Image
(http://i.imgur.com/FdIqIS0.jpg)
on Amazon about a week or so ago. I have it hooked up to a script that will run/kill my guitar amp software using Karabiner on OS X. It does the job well, but the switch feels linear and doesn't have any tactility to it. I thought this was kind of odd considering that you can definitely feel the switch on most guitar foot pedals.
I also bought one of these to use for push-to-talk. I can confirm that while entirely functional for this purpose, the travel distance is a bit too long for it to feel "right"; and yes the mapping software is awful.