I know there isn't a good current alternative in the web world, but shouldn't it be a goal to not have to specify pixels anymore? Obviously mobile browsers already largely ignore/change pixel font sizes.
(If you didn’t notice, we are talking about the web here.)
http://www.w3.org/TR/css3-mediaqueries/
A realistic strategy today is to assume a typical desktop monitor by default, since not all popular desktop browsers implement media queries to a useful extent. Then you can add specific CSS sections for hardware with very different parameters, such as screens on mobile devices. Usually being both newer and more in need, mobile OSes and the browsers running on them typically support media queries better, so while not always ideal, this approach works fairly well in practice.
Maybe for copy text it's ok, but not for other page elements, ones that we want to align in a specific way to bitmap images, no.
The page-zoom style resizing is our best bet --it's the "resolution independent" way to have your pixels and eat them too.
Now, if we could provide bitmap assets that could be zoomed in the same way, instead of just showing bigger but more pixelated (as we can in application icons in OS X), we would be done.
The most common way (used for icons) is to provide multiple bitmaps and load the right one depending on screen DPI. You can do this on your site too.
And there's of course vector graphics (SVG), if you don't mind some extra processing on the client for rendering...
As for SVG, client rendering time would be insignificant for most case (for a desktop machine at least, they have CPU to spare). But currently used IE version (> 6) for one don't support SVG. And the main problem are bitmap assets such as photographs. Those cannot be done as vectors.
