relation to the fireez extension?

Well, I think that the person doing the fireez extension wanted to use the same method to display stuff as the firephp extension - using the multi-part capabilities of firefox to send additional information to the firebug console in the headers. Which might be a way to go and maybe even a way to get more precise information (for instance the line number capabilities of firephp will always return the line number where it is being displayed in the ezfire extension).

But, I was keenly interested in firephp when it first came out and have been trying it out since then and this extension is the result of refining that for the past 8 months or so.

I saw the fireez extension too when it first came out and was interested in seeing how that would work out, but, as far as I can see nothing was ever developed. The idea there was primarily to display ezpublish error message in the console and while I did play around with that I don't find that very useful. To get template variables in the firephp console has been useful as has the ability to dump output to a file to debug php code without having the debug output mixed in with all the other ezpublish debug messages.