if you could get your hands on an html rendering engine that you can run from the commandline, then you can have php simply activate that script.
i don't know any offhand but sound like something the mozilla crowd would be up to... linux desktop environments like kde and gnome (like windows) have an option where you can preview rendered html instead of a stock icon for .html files... so if you wanna search those mailing lists it might help
sorry i don't know naything specific, happy hunting