Drupal_code_sniffer is a project mainly written in PHP, it's free.
PHP Code Sniffer Standard Definition for Drupal
Drupal Coding Standards Sniffer for PTI
More infos about this "Project": http://drupal.org/node/897116
Requirements: Eclipse : http://www.eclipse.org Eclipse PTI (Php Tools Integration) : http://www.phpsrc.org
Installation:
Now you'll have a PHP Tools entry in the right click menu in the navigator. Or you can just hit "Validate" within the right click menu of a file.
Recommendation:
Attention: This is still a draft!! Please cross check with http://drupal.org/coding-standards and http://drupal.org/project/coder if the validation is correct
Known Issues: Documentation Tags just rarly supported - there are many missing / disabled sniffs