GoodNight is a utility that watches your download or upload speed. If speed drops to (or below) a user defined value, it sends your Mac to sleep. So just start your download or upload and go to bed. Your Mac will too, when it is finished.
What's new in GoodNight
Version 1.2:
The time limit can be set higher (up to 60 minutes instead of 10)
The names of available network ports are listed in the preferences (e.g. "en1 (Airport)" instead of just "en1"
You can choose to watch more than one port at the same time (especially useful if you often switch from Ethernet to Airport. Just watch both.)
Option to start GoodNight activated
Option to keep GoodNight active, after it has sent your Mac to sleep. So on next wake up, GoodNight is active again.
Option to watch the sum of download and upload traffic. If you have a download and upload running at the same time, and don't know which will finish first, use this option.