You can use the [shell] and [aka.shell] externals too. The best way is to tell the computer to reboot using applescript and include your patch/app in the startup folder. Then you can use the System Preferences to determine what to run when you reboot.
There was a great little program called KeepItUp that did all you want and more--email alerts if your app crashes, automatic restarts of same, automatic shut-down/startup, logs… Unfortunately, when I tried their web site at it 404'd, so I don't know if it's still available. I'd give it a Google if I were you, it may be around somewhere else.