One of our developers, Alvaro Videla, released a few weeks ago a Firebug/Symfony extension: FireSymfony. This allows developers to see their Symfony debug toolbar as an Firebug extension, which leaves the page layout unchanged and also brings more UI improvement. This being quite useful for us at the office.
Our support to this extension is part of our company culture; we encourage people to participate and innovate for the company or the community. We will provide resources to Alvaro like design for the plugin and the blog, hosting for the site and time during business hours where he can work on documentation, bug fixing and new features.
Good luck little plugin!