I have installed the excellent WPTouch WordPress plugin. Readers using iPhone and Android smartphones see the mobile theme instead of the desktop theme. There is an option to switch to the desktop theme, but the mobile theme has full functionality, including sharing and commenting.
WPtouch: A simple, powerful and elegant mobile theme for your website. WPtouch automatically transforms your WordPress website into an application-like theme, complete with ajax loading articles and effects when viewed from the most popular mobile web browsing devices like the iPhone, iPod touch, and Android mobile devices.