This repo brings this Gist to npm.
var FirebaseRx = require('firebase-rx');
var source =
new FirebaseRx("https://<your firebase>.firebaseio.com")
.observe('<event type>');
console.log(source instanceof Rx.Observable);
source.subscribe(function (changeData) {
// If event type is 'value', changeData is a DataSnapshot
// Otherwise, changeData is:
// {
// snapshot: DataSnapshot,
// prevName: optional string of previous child location
// }
});