in reply to web-based installer wanderings
Not quite the same approach, but a project I've created is something along the same lines. My application framework contains a built in tool to automatically bundle up the entire application into a single self contained 'install.pl' script. Build a web app, run the 'package' command, give to the world.
My installer is command line based at the moment. When run it self unpacks, checking for app requirements (the installer is core pure perl, but the web app itself may have other requirements), creating directory structures and files, setting owner/groups and permissions. It also walks through creating databases if required (MySQL at the moment - db and admin user), generating an initial app config file and sample config files that can be copied more or less verbatim into a webserver setup. Some day I hope to expand it to swing both ways so the user has a choice of either running from a shell, or from a browser (ala php). I think that makes me the other side of your coin, so I hope we can learn something from each other :)
It's a work in progress, but you can check out my installer here: Aqualung Sample Web App
By all means PM me if you want to talk more.