I think your question isn't really about sudo per se, but about auth-as-self instead of auth-as-root. This is often a better choice than no-auth-at-all, particularly for desktop machines -- I want to be able to let my friend browse in Firefox at my computer and be assured that he won't (accidentally or otherwise) install packages, set the system time, etc.
And the answer is: yes, PolicyKit can do this. You set ResultAny in the policy config file to "auth_self" instead of "auth_admin" -- or to "auth_self_keep", to provide temporary caching of authorization (like the sudo typical config).
consolekit, the tool used in Red Hat derived distributions for root access for GUI (and a few command line) utils before PolicyKit, can also do this.