Knockout Subscribe to any change in observable complex object

You can use the following trick:

ko.computed(function() {
    return ko.toJSON(complexObject);
}).subscribe(function() {
    // called whenever any of the properties of complexObject changes
});

See http://jsfiddle.net/xcajt4qn/3/

The reason why this works is ko.toJSON will recursively read all the properties in the object, therefore making the computed depend on all the properties.