Example of creating binding-like observers that are view-instance specific.

emberjs_example.js

App.hash = Ember.Object.create();

App.theList = [{id: 'item1', value: 1}, {id: 'item2', value: 2}, {id: 'item1', value: 1}];
App.aController = Ember.ArrayController.create();
App.aController.set('content', App.theList);

App.MyView = Ember.View.extend({

  hashBinding: "App.hash",

  stub: function(key, val) {
    var id = this.get('id');
    if (id) {
      if (arguments.length === 1) {
        return this.get('hash').get(id);
      } else {
        this.get('hash').set(id, val);
      }
    }
  }.property('hash', 'id').cacheable(),

  id: function() {
    var c = this.get('content');
    if (c) {
      return c.id;
    }
  }.property('content').cacheable(),

  contentWillChange: function() {
    var id = this.get('id');
    if (id) {
      this.removeObserver('hash.' + id, this, 'stubDidChange');
    }   
  }.observesBefore('content'),

  contentDidChange: function() {
    var id = this.get('id');
    if (id) {
      var c = this.get('content');
      this.set('stub', c.value);
      this.addObserver('hash.' + this.get('id'), this, 'stubDidChange');
      this.stubDidChange();
    }
  }.observes('content'),

  stubDidChange: function() {
    this.notifyPropertyChange('stub');
  },

  click: function() {
    var id = this.get('id');
    var h = this.get('hash');
    var val = h.get(id);
    h.set(id, val+1);
  }
});

handlebar_view

<script type="text/x-handlebars">
  {{#each App.aController}}
    {{#view App.MyView contentBinding="this"}}
      {{id}} says {{stub}}
    {{/view}}
  {{/each}}
</script>

This Gist relates to this question on Stackoverflow: http://stackoverflow.com/posts/10406771