bookmarklet.js

javascript:s=document.createElement('script');s.type='text/javascript';s.src='https://gist.github.com/raw/674826/typekit-colophon.js';document.getElementsByTagName('head').item(0).appendChild(s);void('')

typekit-colophon.js

function findTypekit() {
    var a = document.getElementsByTagName('script');
    var y = '';
    for (var i = 0; i < (a.length - 1); i++) {
        var x = a[i].getAttribute('src');
        if (x) {
            if (x.search('use.typekit.com') >= 1) {
                y = 'http://typekit.com/colophons/' + x.substring(23,30);
            };
        };
    };
    if (y != '') {
        window.location.assign(y);
    } else {
        void(y);
        alert('This site doesn\'t use Typekit!');
    };
}

findTypekit();