Viewport Genie
Adds the "real" viewport width and height (in px and em) as an element on the body to help with obtaining values for responsive breakpoints
Use it in conjunction with mqGenie (https://github.com/stowball/mqGenie) to trigger the correct breakpoints in non-WebKit browsers and Chrome/Blink since 29.0.1547.57.
Usage:
Use the bookmarklet to quickly get the viewport size on any page: http://stowball.github.io/Viewport-Genie
Or include viewport.genie.min.js in your page somewhere after the opening <body> tag, and trigger it with a querystring parameter of genie=true