Google announced on its blog a future update including Gmail functionality People Widget, It's actually a Widget "social" that is on the right of an email which includes several contact information that you reply,
Next to every email message you can now see contextual information about the people in that conversation including recent emails you received from them, relevant Buzz posts, shared documents and calendar events. You also have quick access to a variety of ways to communicate with individuals, start a group chat or schedule a meeting with groups of people..Source: Gmailblog