Great suggestion, Hetul. We already have SMS and email alert functionality on this site, but it's not used much. As for sending PNR alerts, the trick is that alerts should be sent only when the position changes. Since we do not have direct access to the PNR database, it would involve excessive polling of the status, which we want to avoid.
However, what we can do is for anyone posting PNR query on the PNR Analysis Blog, to opt in. Then any other logged-in member/admin can explicitly send the SMS alert to the original blogger, based on his/her judgement whether the WL status has changed. We can ponder some variations of this.