This should be possible with the following URL, assuming you're already logged into Gmail:

    http://mail.google.com/mail/#contacts/search/%1

However, there seems to be a bug in the current distribution of Launchy (2.5.0) that prevents it. See here:

- [Using Launchy to search Gmail][1]
- http://sourceforge.net/tracker/index.php?func=detail&aid=2987199&group_id=132975&atid=725839

Claims to be fixed in 2.5.1.  Download 2.6beta release from launchy.net

[1]: http://webapps.stackexchange.com/questions/5506/using-launchy-to-search-gmail