Getting a jQuery selector for an element

Question

In psuedo code, this is what I want.

var selector = $(this).cssSelectorAsString(); // Made up method...
// selector is now something like: "html>body>ul>li>img[3]"
var element = $(selector);

The reason is that I need to pass this off to an external environment, where a string is my only way to exchange data. This external environment then needs to send back a result, along with what element to update. So I need to be able to serialize a unique CSS selector for every element on the page.

I noticed jquery has a selector method, but it does not appear to work in this context. It only works if the object was created with a selector. It does not work if the object was created with an HTML node object.