[lancer383]

Not sure how well adopted it is, but Bourbon CSS's mixin for serving Hi-DPI assets includes DPI-based media queries:

    @media only screen and (-webkit-min-device-pixel-ratio: 1.5),
    only screen and (min--moz-device-pixel-ratio: 1.5),
    only screen and (-o-min-device-pixel-ratio: 1.5/1),
    only screen and (min-resolution: 144dpi),
    only screen and (min-resolution: 1.5dppx) {
      width: 260px;
    }