[Plugin: Google Maps Store Locator for WordPress] automatic radius search

Has anyone been successful adding automatic radius search for closest store based on user’s IP address? What I’l like to do is add functionality to work with this wonderful plugin that will detect the visitor’s IP address, resolve it to their location (lat/long) and automatically determine and display the closest store.

Here is a resource that I found through Google. I would like to add this to my WordPress website.
http://www.snipe.net/2008/12/ip-geolocation-radius-search-in-php/

http://wordpress.org/extend/plugins/store-locator/