Intent intent = new Intent(context, AlarmReceiver.class);
    intent.setAction(AlarmReceiver.ALERT_GUARD_CHECKIN);
    PendingIntent sender = PendingIntent.getBroadcast(context, _id, intent,
            PendingIntent.FLAG_ONE_SHOT);

    AlarmManager am = (AlarmManager) context
            .getSystemService(Context.ALARM_SERVICE);
    am.set(AlarmManager.RTC_WAKEUP, now.getTime().getTime(), sender);

    Intent toCancel = new Intent(context, AlarmReceiver.class);
    toCancel.setAction(AlarmReceiver.ALERT_GUARD_CHECKIN);
    PendingIntent pendingToCancel = PendingIntent.getBroadcast(context,
            _id, toCancel, PendingIntent.FLAG_CANCEL_CURRENT);
    am.cancel(pendingToCancel);