How can I get Knockout JS to data-bind on keypress instead of lost-focus?

Question

This example of knockout js works so when you edit a field and press TAB, the viewmodel data and hence the text below the fields is updated.

How can I chang

Answer 1

Jeff Mercado's answer is fantastic, but unfortunately broken with Knockout 3.

But I found the answer suggested by the ko devs while working through Knockout 3 changes. See the bottom comments at https://github.com/knockout/knockout/pull/932. Their code:

//automatically add valueUpdate="afterkeydown" on every value binding
(function () {
    var getInjectValueUpdate = function (allBindings) {
        return {
            has: function (bindingKey) {
                return (bindingKey == 'valueUpdate') || allBindings.has(bindingKey);
            },
            get: function (bindingKey) {
                var binding = allBindings.get(bindingKey);
                if (bindingKey == 'valueUpdate') {
                    binding = binding ? [].concat(binding, 'afterkeydown') : 'afterkeydown';
                }
                return binding;
            }
        };
    };

    var valueInitHandler = ko.bindingHandlers.value.init;
    ko.bindingHandlers.value.init = function (element, valueAccessor, allBindings, viewModel, bindingContext) {
        return valueInitHandler(element, valueAccessor, getInjectValueUpdate(allBindings), viewModel, bindingContext);
    };
}());

http://jsfiddle.net/mbest/GKJnt/

Edit Ko 3.2.0 now has a more complete solution with the new "textInput" binding. See SalvidorDali's answer