Find out how to activate the new SMS notifications after the break.
To receive notifications via SMS if someone replies to a tweet, go to twitter.com/devices and check the "mentions and replies" option. You can enable reply notifications from only people you follow or from everyone who replies to or mentions you in a tweet. Or, you can turn the feature off completely by unchecking the "mentions and replies" option.
iPhone users can download the updated app now from the iTunes store.