Responsive Design - Howto

Anyone have experience optimizing a responsive designed site.

im foreseeing problems with the size of images, because the dimensions change for each screen size. that clearly clashes with serving an image that matches the width and height when those directives are contained in the css.

short of server code that detects the browser and then adjusts the img tag with the optimized image size.

and i dont think that mod_pagespeed does that. im sure it only does one size, not many.

so… any ideas.