Years ago I wrote about a Firefox extension that allows you to start an Xdebug debugging session by clicking on an icon in Firefox' status bar. For some unexplained reason, this extension is no longer available through Firefox' addon-site. Although I have a copy at http://xdebug.org/files/xdebug_helper-0.3.1-fx.xpi for archival purposes, there are now a few other browser extensions that do the same thing.
easy Xdebug is an extension that serves as a replacement for the now unavailable Xdebug helper extension. It's written by Brecht Vanhaesebrouck of eLime. The extension was originally tested with Netbeans but it also seems to work fine with Komodo.
Xdebug enabler is an extension for Google's Chrome browser. It "allows you to enable and disable triggering Xdebug from with in Chrome. Useful if you are a web developer using an IDE that supports Xdebug like Eclipse with PDT." It's written by 'remailednet' and available through the Google Chrome Extensions website.
Update: The "Xdebug enabler" Chrome Extension seems to have some issues. There is now also an alternative Chrome Extension called Xdebug helper that integrates quite a bit better. You can find it at its Google Chrome Extension page.