But I do have a reasonably stable, working version of the first component of my Real Costs project up on the soon to be relaunched website at TheRealCosts.com. It is a Greasemonkey Script, that will soon be compiled as an .xpi Firefox Extension.
Currently, it is inserting on the CO2 produced per passenger for plane flights. It is working on airplane ticket purchasing sites. I have tested it on a couple, but it is highly likely that it will break (on) others. This is super rough, but working!
Much more development in the next few weeks and months.