[launchd-dev] can i do this with launchd? (on-demand auto-restart daemons)

i am interested in writing a cocoa front end to hellanzb. it is a python program that has a daemon mode. you interact with it via a tcp socket. i want to use launchd to control the daemon. 1. it should start when the cocoa GUI is started (either manually or via a startup item) 2. if the daemon dies for whatever reason, launchd should restart it 3. if the GUI is closed, the daemon should be shut off without having it restart. thank you for your help. ian