Used StartupWP Pro and then customized with a child theme to eliminate issues with future updates.
Specifically though, check out the Rent A CIO page at http://www.praecom.com/rent-a-cio. This uses custom AJAX on the client side to get W3C location info and custom PHP to redirect based on location to a specific city based page. Will tell you that if you are outside the St. Louis MO metro area, or Illinois or Missouri it looses some of it’s “zing”.
You may want to add a CSS popup to http://www.praecom.com/rent-a-cio/ to be even more clear to the visitor that it’s redirecting, as it’s a little slow and could result in some people clicking “Back” in their browser.