Auto logout Gnome desktop on idle?

[Masao Kitamura]

Hello,

I want to have Gnome Desktop auto-logout users when they're idle for X minutes.

Does anyone know how to do this?

I've tried the "autolog" package, but that seems to only work on
non-GUI terminals.

How does the screensaver know how long the user has been idle?  Is
there a system variable and/or built-in utility?

Thanks,

Masao

Ubuntu 10.10 32-bit on HP xw6400 Workstations