This plugin exposes selected menu with its items and their properties as a context condition. Purpose of it is to create a Context on a menu if selected depth, router_path, has_children or other specified menu item internal values are met for menu items in active trail.
I used it along with the Menu Block module to provide replacement block if custom (Menu Block) block is not visible. For example, if there are no children menu items of 2nd level to render in sidebar navigation block, context is active and Block reaction is set with replacement block.