Easy Video Background lets you add video in the background of your website with a single jаvascript call. The script automatically picks the most optimal video format based on the browser where it is being run in. Furthermore it has a built in image fallback for mobile devices where it is not possible to have video playing as a background. When the HTML5 video tag is not supported, a Flash fallback will make sure the video will be visible.

Demo: http://codecanyon.net/item/easy-video-background/1365012