Sorry for the delay, I've been busy at work a lot recently...
Here you go... 4121
As above application but with 30 second dialog...
Remove power and either wait 30 seconds or tap OK to shutdown...
Or tap Cancel to continue on battery...
Or restore power to close dialog box...
Run Auto Power Off to start/stop process!
To personalise the message or change the timer open Select.mscr and edit the bold text
ChoiceDefault ("Device will shutdown soon...", "External power disconnected, Device will shutdown soon...", 1, 30, "Tap OK to shutdown now or Cancel to continue...")
The text may not wrap on to the next line so keep it short!