foo.js

App.Bands = Ember.ObjectProxy.extend();
App.Bands.reopenClass({
  all: function() {
    return $.getJSON("http://domain.com/api/v1/bands?format=jsonp&callback=?").then(function (response) {
        return response.map(function (band) {
          return App.Bands.create({content: band})
        });
    });
  }
});