The first attempt at writing a web application proxy that is supposed to be used in a team.
(I'm first going to write down some thoughts here, until I'm in a state were I'm confident what I can write a lot of code).
When currently looking into a page, all inforamtion is stored locally on your machine. While most tools have embraced collaboration, information isn't shared. Now one could simply install some proxy on a vm somewhere and tell everyone to proxy their traffic through there, this isn't really practical.
In the end, what I imagine would be a proxy that allows you to view the results locally (requests send and so), but for all people of the team. You should still be able to use it in "singleplayer" mode, but should also be able to function as a "shared host" that syncronizes the state of the application with other people.
The simplest one: we're all in the same network and we all want to work with each other. Open some port in your firewall allowing your instance to communicate with another one.