That wouldn't disable outbound caller ID. It would just change it (to the GV number) if the person used Google Voice for outbound calls.If you are using Google Voice you can add the widget... simply add a shortcut to your home screen "Toggle Google Voice." Thats the only one I know of though.
Tasker might be able to do this but if you're looking for an "appliance" app Tasker probably isn't the best choice.
That wouldn't disable outbound caller ID. It would just change it (to the GV number) if the person used Google Voice for outbound calls.