The best way to do it is with launchd, it's not quite as simple as a login or startup item, but by creating it in /Library/LaunchDaemons it can run as root.
The file you'd want to create would look something like:
Code:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>Label</key>
<string>com.pmset</string>
<key>ProgramArguments</key>
<array>
<string>pmset</string>
<string>womp</string>
<string>0</string>
</array>
<key>RunAtLoad</key>
<true/>
</dict>
</plist>
Just create the file in that format under something like:
/Library/LaunchDaemons/com.pmset.plist
This should cause it to run invisibly, and you can use the label of com.pmset to check that it's running in the Console.
While it's a bit more of a learning curve, I think that launchd is the best way to run anything at start-up, on a specific date (daily, weekly etc.), or for watching out for volume changes (mount) or folder updates. I use it now for all sorts of things, including setting the noatime flag on some volumes, checking if Macports needs updating and so-on.