It requires the precise geo localization plugin (#45). We could plot the last N visitors on a google maps with the exact position of the visitors. A click on the dot could show basic information about the visitors.
One problem I see here: The terms of service for Google Maps forbid you from using their maps on any internal (i.e. not accessible to the general population) website.
IMHO it would be better to utilize the OpenStreetmap project for this purpose. Using Yahoo Maps may also be an alternative.
No dependency with third party providers, please.