howto boot with a single gui app as the desktop ?

[David Timms]

I would like to configure an fc6 system so that it:
- logs on without user interaction
- runs only one application {vnc viewer - which asks for the name of a 
machine to connect to}
- if the viewer is exited, then vnc viewer should restart, waiting for a 
machine to connect to.
- has a way to exit the viewer.

I haven't had any luck with searching for "linux single app" and the 
like. What are the technical terms for this sort of configuration ?

Any pointers to information in this area would be very welcome ;)

Thanks, DaveT.