Taken from http://stackoverflow.com/a/18526757 but I want a copy to keep around.

count_angular_watchers.js

(function () { 
    var root = angular.element(document.getElementsByTagName('body'));

    var watchers = [];

    var f = function (element) {
        angular.forEach(['$scope', '$isolateScope'], function (scopeProperty) { 
            if (element.data() && element.data().hasOwnProperty(scopeProperty)) {
                angular.forEach(element.data()[scopeProperty].$$watchers, function (watcher) {
                    watchers.push(watcher);
                });
            }
        });

        angular.forEach(element.children(), function (childElement) {
            f(angular.element(childElement));
        });
    };

    f(root);

    // Remove duplicate watchers
    var watchersWithoutDuplicates = [];
    angular.forEach(watchers, function(item) {
        if(watchersWithoutDuplicates.indexOf(item) < 0) {
             watchersWithoutDuplicates.push(item);
        }
    });

    console.log(watchersWithoutDuplicates.length);
})();