Issue when trying to listen to iBeacons #235

When I try to run the javascript below, I get this error:

10-12 22:22:56.329 17624-17624/? W/ScriptView﹕ Uncaught Error: Error calling method on NPObject. -- From line 1 of

JavaScript code:
WS.sensorOn(WS.sensor("ibeacon"), 1000);
WS.subscribe('ibeacon', function (channel_name,UUID,powerLevel,majorNum,minorNum) {
WS.log("ibeacon found with uuid:" + UUID);
});