Josh Pollock

Use this plugin to create a demo site for your themes, or use it to allow users to customize the presentation of your site.
The JP Theme Bar Plugin adds a theme switching bar to the bottom of your site, perfect for theme preview sites. The settings page for the plugin lets the end user choose which themes to add, as well as set the colors for the theme bar. You can see it in action on this site.
New in version 0.0.3 -> Themes will update theme mods when changing themes allowing for individual theme settings to be previewed properly.
This plugin is based on the <a href="http://iainjmccallum.com/wordpress/live-demo-theme-bar/" rel="nofollow ugc">IJM Theme Switcher Bar v2.0</a> by <a href="http://www.iainjmccallum.com/" rel="nofollow ugc">Iain J McCallum</a>
IMPORTANT- The plugin <a href="https://wordpress.org/plugins/theme-test-drive/" rel="ugc">Theme Test Drive</a> by <a href="http://www.prelovac.com/vladimir/" rel="nofollow ugc">Vladimir Prelovac</a> must be installed and activated in order for the theme switching to work.

JP Theme Switcher Bar

Adds a theme switcher/ theme demo bar to the bottom of your site to allow users to switch the theme they see on your site.

Seth Smigelski

Ever wanted to serve a dedicated theme to visitors on handheld devices instead of a theme that is fine-tuned for big screen traffic?
Slim Mobile Theme Switcher is a highly optimized, lightweight plugin designed for websites that need to serve a different theme to mobile devices while preserving the primary desktop experience.
Instead of relying on clunky, resource-heavy device detection libraries, this plugin uses streamlined, modern user-agent detection to instantly route users to the correct theme before the page even loads.
<h3>Key Features</h3>
<ul>
<li>Three-way Theme Routing: Serve up to three different themes simultaneously. Set one theme for Mobile Phones, one for Desktops, and optionally enable a dedicated theme specifically for Tablets (iPads/Android tablets).</li>
<li>True Mobile Detection: Uses refined regex to separate small-screen phones from tablets (iPads/Android tablets).</li>
<li>Zero-Friction Setup: Select your themes from a simple dropdown menu. No coding required.</li>
<li>Manual Overrides: Allow users to manually switch between views using <code>?theme=handheld</code> or <code>?theme=active</code> or <code>?theme=tablet</code>.</li>
<li>Persistent Choice: Activating the ‘Remember Visitor’s Choice’ option ensures that when a user has manually selected a different theme, this preference is saved for 30 days via cookies.</li>
<li>No Bloat: Zero front-end CSS or JS added by the plugin itself.</li>
<li>Developer Friendly: Built by a developer for developers.</li>
</ul>

Slim Mobile Theme Switcher

Serve a lightweight mobile theme to phones while keeping desktops on your primary theme. Includes dedicated tablet routing.

JP Theme Switcher Bar vs Slim Mobile Theme Switcher