Try uMatrix! That's almost exactly what it does. Further, it lets you control requests by type, like stylesheets, images, scripts, XHRs, iframes, etc. Its orig

Try uMatrix! That's almost exactly what it does. Further, it lets you control requests by type, like stylesheets, images, scripts, XHRs, iframes, etc. Its original name was HTTP Switchboard, which I thought was a great descriptor for what it does (and for its interface).