Don't put ko.observable
directly into your ko.observableArray
but create objects which have observable properties.
So change your array filling code to:
var val = ko.observable(obj.val);
that.obs.push({val: val});
And your view to:
<ul data-bind="foreach: inputs">
<input type="text" data-bind="value: val" />
</ul>
Demo JSFiddle.