It's not the best test in the world but it suffices for me to yepnope load the CSS3 Media Queries lib from Google Code. Will eventually look at optimising it as it's 75% copy and paste from an unknown source

css3-media-queries-test.modernizr.js

Modernizr.addTest('css3mediaquery',function(a,b){var a=document,b='screen and (min-width: 1px)',c={},d=a.documentElement,e=a.createElement("body"),f=a.createElement("div");f.setAttribute("id","ejs-qtest"),e.appendChild(f);return function(g){if(c[g]===b){var h=a.createElement("style");h.type="text/css";var i="@media "+g+" { #ejs-qtest { position: absolute; width: 10px; } }";h.styleSheet?h.styleSheet.cssText=i:h.appendChild(a.createTextNode(i)),d.insertBefore(e,d.firstChild),d.insertBefore(h,d.firstChild),c[g]=f.offsetWidth==10,d.removeChild(e),d.removeChild(h)}return c[g]}});