Rapportive, a Gmail add on for inbox social intelligence, joined with Gmail's people widget increasing social integration, particularly Twitter integration for Gmail inboxes. Their Twitter widget now lets you follow your email contacts, send them replies or retweet them, and even mention them inside email messages. You can also take a look at whether your email contacts are following you on Twitter or not.
Use Twitter in your Gmail
The feature also works with Twitter's notification system where when you get a message that someone is following you on Twitter, you can follow them back from within the email message itself. Previously, the widget only highlighted recent tweets from contacts, but now, the system is almost like its own third party application for Twitter, where you can basically use most of its functions right from the inbox.