MultiRatings/Location Manager modification

I need a modified version of the MultiRatings and/or Location Manager add-ons. This includes creation of widget that can be placed on a page that shows a list of restaurants along with their star rating within x number of miles of a user’s location (x will default to 5 miles, but can be changed by the user). The list should look something like this: http://www.screencast.com/t/dd1Gk6RW1

If the user clicks on the restaurant name, they’ll go to the restaurant’s profile page.

I also need advice on server requirements to handle approximately 500,000 records and potentially high volume of traffic.