As Pieter suggested, this is a great treat for those looking to communicate with Javascript from Flex. But since links can break, let me explain it a bit here:
In Javascript
document.location = '$' + 'Data#As#String';
In Flex
webview.addEventListener( LocationChangeEvent.LOCATION_CHANGING,
handleLocationChanging );
function handleLocationChanging( event:LocationChangeEvent ):void
{
event.preventDefault();
//location parameter will have a absolute path of the .html file as a prefix
var strParameters:Array = (e.location as String).split("$");
trace(strParameters[1] + "Is the string received from Javascript");
}