title: How can I bind the radius of my Geofire query in AngularFire?
body: <p>I have a model in <code>angularJS</code> which is bound to firebase <code>$scope.items=$firebase(blah)</code> and I use <code>ng-repeat</code> to iterate through the items. 
  Every item in firebase has a corresponding geofire location by the key of the item. </p>
  
  <p>How can I update my controller to only include items by a custom radius around the user? I don't want to filter by distance in angular, just ask firebase to only retrieve closer items (say 0.3km around a location). I looked around geoqueries but they have a different purpose and I don't know how to bind them to the model anyway. The user may change the radius and the items list should be updated accordingly, so they need to be bound somehow.</p>
  
  <p>Any suggestion is welcome, but an example would be greatly appreciated as I don't have fluency in this trio of angular/firebase/geofire yet :P</p>