Celebrity Tweet Alert

What is the best way to find out when a celebrity has tweeted so that you can be the first to reply?

I'm talking any alert system like RSS, application integrated into Slack, smart phone alerts and so on; anything.

Impressions go up considerably when you are one of the first, if not the first, person to reply to a celebrity tweet.

I've got a list of accounts in mind, just wondering how best to get the alerts.