Changing a tab/window's document title when it isn't in focus. Supports modern browsers, in theory. Does nothing in older ones, hopefully.

titlechange.js

/*
 if the browser supports it, and the page isn't in focus (tabbed away, etc)
 we change the title to whatever is passed into the anonymous function, 
 as a reminder.
 */
(function(hidden_title, undefined) {
    var has_document;
    var has_title;
    var has_event_handler;
    var original_title;

    has_document = window && window.document !== null;
    if (has_document === true) {

        has_title = window.document.title !== null;
        if (has_title === true) {

            original_title = window.document.title;

            has_event_handler = document.addEventListener !== null;
            if (has_event_handler === true) {

                var change_title = function() {
                    var is_hidden = window.document.hidden !== null && window.document.hidden === true;
                    if (is_hidden) {
                        if (hidden_title !== void(0)) {
                            window.document.title = hidden_title;
                        }
                    } else {
                        window.document.title = original_title;
                    }
                };
                document.addEventListener("visibilitychange", change_title, false);

            }
        }
    }
})('MY AWESOME TITLE YO');