How to create a notification just after shuts down?

Question

I need to turn of my audio monitors before shutdown, but sometimes I forget.
I would like to see a notification (created by me) every time I shutdown

Answer 1

There are a number of ways of scheduling a task at shutdown, but the easiest is probably even easier - just write a stay-open application script that does nothing until it's quit at which point it posts a reminder dialog.
on idle
          return 10000
end idle
on quit
          display dialog "Don't forgt to turn off all your other gear" buttons {"Got it!"} default button 1 giving up after 60
          continue quit
end quit
the idle handler is just a dummy to keep the process alive, the real work is in the quit handler which posts a dialog and then continues the shutdown process. the 'giving up' parameter makes sure the app doesn't stall the shutdown process - it's better to shut down the Mac, even if you forget to shut off the other stuff, than it is to leave everything running.
Save this script as an application and set it to launch at login.