line length marker now with Jquery inclusion built in

compressed version

javascript:!function(){var a=document.createElement("script"),b=function(){var a=$("p"),b=0,c="",d="";for(b=0;b<a.length;b++)c=$(a[b]).text(),d=c.slice(0,45)+"*"+c.slice(45,70)+"*"+c.slice(70),$(a[b]).text(d)};a.src="//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js",document.getElementsByTagName("head")[0].appendChild(a),setTimeout(b,500)}();

source.txt

javascript:!function(){
  var jq = document.createElement('script')
      , insertMarkers = function(){
        var a=$("p")
            ,b=0
            ,c=""
            ,d="";

        for(b=0;b<a.length;b++){c=$(a[b]).text(),d=c.slice(0,45)+"*"+c.slice(45,70)+"*"+c.slice(70),$(a[b]).text(d)};
      };
      
  jq.src = "//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js";
  document.getElementsByTagName('head')[0].appendChild(jq);
  
  setTimeout(insertMarkers, 500);
  }();

A quick and dirty script to put line length flags (*) in all the paragraphs on a page for working with responsive breakpoints.

turned it into a link so you can grab either revision one (the raw js) or revision two (the link version)

Paste the code as the URL for your bookmark in the bookmark bar of your browser and then you can use it on any site. Requires jQuery at the moment.