Is there an automated deployment tool that manages startup applications on a variety of machines, especially the Unices? Or is the only hope to study the nuts and bolts of each Unix (osx, linux, solaris, hpux, aix) on how to configure applications to launch on system startup?

I want to run them as a specific user, instead of root. At the moment, I run them all within a screen session .. which is a hassle, as this requires manual intervention every time the machine is rebooted for some reason.

Ideally, I am looking for a tool that would read, say, ~/.startup-programs which file contains, on each line, the command line to launch the needed daemons. And this tool should work on OSX, Linux, Solaris, HPUX and AIX ... writing the appropriate startup scripts for each platform.