Smart Iframe takes KCSG Kartra Pages and Kartra embed codes several steps further, allowing you to almost seamlessly mix content from different sources within a page. For example, you can display content from a Kartra account mixed with other content on WordPress pages (even if there's no Kartra embed code for it) or display content from a WordPress installation mixed with other content on Kartra pages.
The technology is platform-agnostic and can be used on, or with content from, other platforms as well (any place you can add custom HTML to the parent and child content pages).
Smart Iframe is available in standalone and WordPress versions. The plugin included with the WordPress version allows you to conveniently access the scripts and additional WordPress-specific functionality via short-codes.