Possible Duplicate:
Change cursor shape (or color) to indicate vi mode in bash
I am using vi-mode in a bash shell, and I would like to change the PS1 variable whenever I am in insert mode. When I run bind -v | awk '/keymap/ {print $3}', the result is vi-insert for insert mode and vi for normal mode.
I would like some visual indicator of which mode I am in, such as a yellow prompt or a dot, something like this:

I would like this visual change to happen as soon as the mode changes, even if no command is run. Is it possible to change the value of PS1 for the current process and update the prompt without hitting enter?