Charles (http://www.charlesproxy.com/ http://www.charlesproxy.com/) has been a permanent addition to my toolkit for this exact reason. Cross platform, cross bro

Charles (http://www.charlesproxy.com/ http://www.charlesproxy.com/) has been a permanent addition to my toolkit for this exact reason. Cross platform, cross browser HTTP monitoring and proxying with throttling and all sorts of goodies. I believe there are several pure-CLI ways of doing this as well, but Charles is $40 well spent.