Pngy is a bit of jQuery that allows you to load images of different file sizes based on a page’s load speed. So, if the load speed is slow, Pngy can load your small image. If it’s fast, it can load a hi-res image. It’s kinda like a ping test in Javascript.
Resonates with my ideas on responsive images
via bram.us
Before we have a real solution like the proposed element, plugins like pngy will make life a little better for us