Google-chrome – How to open a page in Chrome from the command line, in a new tab or an existing tab as appropriate

I'm looking for a way to open a given page in Google Chrome from the command line, with the following behaviour:

• If the given page is already open in a tab, navigate to that tab
• If the given page is not already open in a tab, open the page in a new tab and show that tab

Currently when I open a URL from the command line (e.g. using "open http://godzillahaiku.tumblr.com" on Mac OS X), Chrome will always open the URL in a new tab. I end up with lots of duplicate tabs as a result, which is a minor annoyance.

I'm looking for a solution that works on Mac OS X, but a non-OS specific solution would be preferable.

I'd consider writing a Chrome extension for this if there's no existing solution.