Search Radius

I need to find a plugin or hack to be able to create a search form that will allow us to search a registered user by radius.

We are currently using the Front End Pro plugin which has a user registration form cutom field that has a google map thing. So I’d assume they can place their location marker there. But I need to create a search page that allows our sites visitors to locate these users by using a search field and saying within 20 miles of Los Angeles or something. The actual map and markers being displayed isn’t the most important to me as I’d like to create our own “listings” styled results on a page. I just figure that using google maps location data is probably the easiest and most accurate way.

Any recommendations, ideas, plugins, hacks, etc?

Thank you so much for the help!