Android - Identify if a user is online in Google Hangout

Hangouts doesn’t use the green or grey dots that Google Talk used to identify if someone is online or offline. Instead, you can tell if a contact is online or not if their profile picture is clear or faded. A faded profile picture means your contact is unavailable, and a clear picture means they’re online. One downside is that Hangouts doesn’t support the “invisible” status like Google Talk did

Just released today, version 1.2 says this in the "What's new" section:

• You can finally see who is on Hangouts! When you start a new Hangout, green icons show who's on, and gray shows who's not.

Also of note:

• Contacts are now organized by People you Hangout with, Suggested People, and Other Contacts.
• Long press contacts in the New Hangout screen to hide them.