With bartender, or other bar add-ons, you can easily stick a spell/action on a button, hotkey the button and hide the bar or button. This should serve your purpose.

I currently use Keyclone, it works for me.

I will try out ISBoxer at some point, but at first glance it seemed onerous to migrate to, especially across multiple computers, so I temporarily shied away from it. It looks good though.