Q:

Handlebars/Ember.Checkbox - 2 bound checkboxes, one checked on false

I'm working on an RSVP form in an app, and I'm trying to figure out how to have two checkboxes mirror each other, when one is checked the other is not. Right now, my approach has been to have each checkbox bound to the isComing property, with one being checked on !isComing, but it's not working that way.
Here's what I tried:
HTML:
<script type='text/x-handlebars'>
<label>I&#39;m coming!</label>
{{view Ember.Checkbox checkedBinding="isComing"}}
<label>I can&#39;t make it.</label>
{{view Ember.Checkbox checkedBinding="!isComing"}}

{{#if isComing}}
<p>The rest of the form will be here.</p>
{{/if}}
</script>

JS:
window.App = Ember.Application.create();

App.ApplicationController = Ember.ObjectController.extend({
    isComing: false
});

This doesn't work. The first checkbox works fine, but the second checkbox is completely unaffected. Clearly, !isComing is not allowed...
This would be trivial to do in jQuery, and I thought about created a computed property that the second checkbox is bound to and that listens to isComing, but those don't seem like the right way.
Is there an easier way to do this with Handlebars or Ember? Here's the fiddle if you want to experiment.

A:

If you can use a radio button, then I'd use this dude's implementation (http://thoughts.z-dev.org/2013/07/04/radio-buttons-in-ember-js/), simple and clean
App.RadioButton = Ember.View.extend({
    tagName : "input",
    type : "radio",
    attributeBindings : [ "name", "type", "value", "checked:checked:" ],
    click : function() {
        this.set("selection", this.$().val())
    },
    checked : function() {
        return this.get("value") == this.get("selection");   
    }.property()
});

http://jsfiddle.net/3aZzn/2/
That being said, Adam's answer is just as good if you don't mind one being checked up front.

