This won't work for some standard stuff that OS X ships with, for instance Python (when started as a command-line interpreter). That's because .inputrc is read by the GNU readline utilities, and Apple links with the BSD equivalent.

To make this work for Python:

Add a file called .editrc with the following content:

bind -v

Add a file called .pythonrc with the following lines:

import rlcompleter import readline

Add a line to your .bashrc which makes Python run .pythonrc when it starts interactively:

export PYTHONSTARTUP="$HOME/.pythonrc"

Now Python will understand your vi keystrokes :-)