Edit in JSFiddle

var timer = new koTimer(180, {
    notifyTimeMarks: [60, 120],
    callback: function () {
        $('#timer').html('<span class="fin">Time is up!</span>');
    }
});

ko.applyBindings(timer, $('.main')[0]);

<div class="main">
    <div id="timer">
        <div class="label">Time left:</div><span data-bind="text: TimeLeftStr"></span>
        <br>
        <div class="label">Time elapsed:</div><span data-bind="text: TimeElapsedStr"></span>
    </div>
    <button data-bind="click: stop">Stop Timer</button>
    <button data-bind="click: start">Start Timer</button>
    <button data-bind="click: reset">Reset Timer</button>
</div>