Google Toolbar
Google Toolbar API

Create Your Own Buttons for the Google Toolbar

Custom Buttons

The Google Toolbar API lets webmasters create custom buttons for the Google Toolbar (version 4 and above) using XML. Buttons can navigate to and search a site, display an RSS feed in a menu, and change their icon dynamically. Users can add your custom buttons to their Toolbar by clicking on a link on your website or Google's Button Gallery.