Have you tried using the @media rules in your CSS? You can target different media sizes easily this way.
Here are the blocks in my .less file for sourcecoast.com to give you an idea of the sizes for different devices.
@media (min-width:1200px) {...}
@media (max-width:979px) {...} /* Up to small desktop */
@media (min-width:768px) and (max-width:979px) {...} /* Tablet to desktop */
@media (max-width:767px) {...} /* Landscape Phone to Tablet/Desktop */
@media (max-width:480px) {...} /* Up to Landscape Phone */
-Melissa
Module class suffix: making module appear only on mobile/phones.
