docs: public static void onCreate(Context context) {
          sContext = context;
          context.registerReceiver(ALARM_BROADCAST_RECEIVER, new IntentFilter(PING_ALARM_ACTION));
          sAlarmManager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
          sPendingIntent = PendingIntent.getBroadcast(context, 0, new Intent(PING_ALARM_ACTION), 0);
          sAlarmManager.setInexactRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP,
                  SystemClock.elapsedRealtime() + AlarmManager.INTERVAL_HALF_HOUR,
                  AlarmManager.INTERVAL_HALF_HOUR, sPendingIntent);
      }