private ServiceTracker tracker;
public void start(BundleContext context) throws Exception {
tracker = new ServiceTracker(context, TemperatureSensor.class.getName(), null);
tracker.open();
SchedulerCallback service = new SensorScheduledService(tracker);
Dictionary<Object, Object> properties = new Hashtable<Object, Object>();
properties.put(SchedulerCallback.SCHEDULE_PERIOD_IN_MILLISECOND, 1000L);
context.registerService(SchedulerCallback.class.getName(), service, properties);
}