Here is some other info that might interest you.
GKSu is a library that provides a Gtk+ frontend to su and sudo. It supports login shells and preserving environment when acting as a su frontend. It is useful to menu items or other graphical programs that need to ask a user's password to run another program as another user.
gksu is a library and application used to ask the user for passwords to run programs as root. It is not a good option now that we have PolicyKit. Still, we still have applications which are not written to take advantage of the PolicyKit framework, and since making applications use it usually involves structural changes, a new version of gksu will provide functionality similar to the one provided by the current gksu to cover applications which still haven't been patched to use PolicyKit. The new gksu will use PolicyKit as backend, instead of su and sudo. This page intends to work as a notebook for planning/designing that new version.
PolicyKit is an application-level toolkit for defining and handling the policy that allows unprivileged processes to speak to privileged processes: It is a framework for centralizing the decision making process with respect to granting access to privileged operations for unprivileged applications. PolicyKit is specifically targeting applications in rich desktop environments on multi-user UNIX-like operating systems. It does not imply or rely on any exotic kernel features.