We've just released a mobile extension which based on this plugin: BlackRed Flatlia. Now you have a great built in mobile template + mobile detector plugin. Check it out here:
The detector script is based on mobileESP:
How To Install
1/ Download the plugin by click here: http://www.blackreddesigns.com/products/joomla-mobile-detector
2/ Install it as a Joomla! 2.5/3.x extension
3/ From Plugin Manger -> find the plugin (Mobile Detector) -> Enable it + Make sure that the option "Enable Template Switcher" set to YES - Select the template to apply when switching
4/ Save it. Then use a mobile device and browse to your Joomla! website to check and see that the switcher just work!
I am using 2.5.9 and installed the plugin at the last position as detailed in the documentation.
We have just released a new version with may fixed your issue. Try it now :)