Many people use no-ip.com to run servers on dynamic IPs. This file allows the Linux version of the No-IP client to be run as a system startup service. This means that it stays running without anyone logged in, and uses next to nothing in system resources.
An added benefit is that it may also be used to find stolen systems by passing the IP alone to the police. I created this package personally.
[robg adds: I haven't tested this myself, but I did verify that the package doesn't seem to contain any malicious code.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030610080204739