The Adaptive image module provides device-appropriate versions of images from your fields.
You can activate adaptive images by adding an adaptive effect to any of your image styles.
The used technique is derived from http://adaptive-images.com/ by Matt Wilcox.
The hard work is done by Drupal core no need for any additional rewrites.
If image styles work on your website, this module will too.
For additional information on Responsive Webdesign and Fluid Images check out