I've added "Search PubMed" to my Ubiquity commands. It's a rewrite of Thomas Lemberger's earlier command, making use of the JSON response from my Yahoo Pipe.
Note: the command requires a version of Ubiquity which hasn't been released yet, as it uses Utils.setTimeout and Utils.clearTimeout to introduce a 1 second delay, reducing the number of calls made to the Yahoo/PubMed web services. You can get the most recent source from the Ubiquity Mercurial repository:
hg clone http://hg.toolness.com/ubiquity-firefox
Aside: it's a bit annoying that you can't use jQuery's text() and html() commands to build the output HTML, and it seems that setting "json" as the response datatype doesn't work either.