Is it also for you a routine to look up the documentation for Drupal hooks at api.drupal.org? If you also use TextMate and are sick of having to command-tab to your browser to get to the documentation, then you’ll have a much better alternative in about 15 seconds.
Go to Bundles → Bundle Editor → Show Bundle Editor. There, click the plus-button in the bottom left corner to add a new command. Set the input to None, the output to Show as Tool Tip and the scope selector to source.php. Copy/paste the command below and assign a shortcut — I use CTRL + D.