Unlock Mac from Terminal or Automator
It is not possible anymore in OSX 10.8 the only option I can think of is to disable your password from the lock screen manually in:


  System Prefs > Security > General > Require password


But you have to have fileVault disabled as well maybe below then does work for 10.8?

Edit: I've tested the code below in OSX 10.8 and below doesn't work for 10.8 :(

So make sure this runs before the rest ( and maybe even add a location check to disable authentication when you are at home or connected to your wifi network )

In applescript:

tell application "System Events"
    set require password to wake of security preferences to false
end tell


or

do shell script "defaults write com.apple.screensaver -int 0"


To enable the settings again use true or 1.