I have finished one of my few projects - Daysleeper.
You can shut down (or reboot) your machine at the time you specify: an exact time or an amount of time to countdown.
It's configurable via tooltypes or CLI/Shell. All options are described in the Readme. The source code is included.
It's already available on Aminet.
There are plans for future:
- a kind of configurable progress bar
- top bar menu
- help bubbles
- a blinking icon (while iconified) at the end of countdown
Hope it will become useful for you.