Parallels Themes Switcher

In short, this plugin allows you to modify/switch the current theme with live site on the fly without messing up with your current visitors.
This plugin is perfect for WordPress theme developers, freelancers as it allows you to edit the live theme without interfering the current visitors.
It offers following features:

• Ability to duplicate any current themes to the new theme for editing purpose.
• Selectively enabling the theme switcher on the frontend by enabling extra settings in the backend. (By role or by IP Addresses)
• Provides an Ajax theme switcher on the right top which selectively allows the visitor (by role or IP Addresses) to switch the theme.
• A transparent banner on the top to display current theme.
• Full Support is available at http://www.xhtmlweaver.com or wp-support@xhtmlweaver.com