While you can use Glass to send messages by email or SMS, the Hangouts Glassware adds flexibility to how you communicate with your friends, and allows you to send photos directly to them from your Glass.
The Hangouts Glassware is automatically enabled when you set up your Glass, and, with it, you can send Hangout messages to any contacts configured to receive messages via Hangouts. Just say "Ok Glass, send a message to..." and the contact's name.
Google Hangouts work across Glass, mobile devices, and your computer. Any message you send will be accessible from your message history on any of these devices, and you can seamlessly switch your conversation between any of them.
You can also use Hangouts to send pictures to your friends, either by tapping on the picture in your timeline and choosing "Send", or by taking a picture with the camera button while you're dictating a message. Go ahead—embed what you're seeing directly into your message!
- Read more about Messaging.