Christoph Dorn has a new post to his blog about a tool he's released to compliment his FirePHP - the FirePHP Companion.
When I originally wrote FirePHP in 2007 I had big ambitions as to the features I was going to incorporate. [...] What I needed was a wholistic approach to the problem area of server-side application intelligence and a set of libraries based on standards that could be applied cross language. After countless hours of research and development I am pleased to announce the first fruit of my labor.
The the post includes all of the instructions you'll need to get this new tool up and working with your site. There's also a screencast on the documentation that walks you through everything too.