I have been recently working on an extension (code name HTTP Monitor) that can be used to intercept HTTP traffic of a browser tab. The extension is based on Firebug's Net panel and is on its way to be embedded in Firefox by default.
This post explains how to use HTTP monitor to intercept HTTP traffic on mobile with Fennec (Firefox for Android) installed.
We have decided to extend cooperation between Firebug and Firefox dev-tools teams (I am a member of both) and so, discussed this topic about four weeks ago at our meeting in London.
We agreed that we want to have an effective and synchronized strategy when working on in-browser developer tools. One pillar of the plan is sharing APIs, components, modules, code maintenance, etc. to avoid duplicate development effort.
The first step is sharing an independent HTTP tracking component that is based on Firebug's Net panel and can be shared among all tools that want to intercept an analyze HTTP traffic. Firebug and (built-in tools in) Firefox will be its first clients.
So take a look at what we have managed to implement and demonstrate for our Toronto meeting last week.