Google Hangouts URI functionality to start Hangouts chat or video call, etc.

We want to add Google Hangouts functionality to our web / client apps. We have a global address book in our browser based web app. For each user, we want to have an icon to start a chat and an icon to start a video call right in Hangouts. We don't want to launch Hangouts Air. It should also work on mobile devices when the Hangouts app is installed.

Ex, Skype offers a link to the API URI , which is actually what we're looking for. This is easy to implement because you can simply set the value of the href attribute of your anchor labels to the Skype URI.

Is this also possible with Google Hangouts? I didn't find anything in the API documentation.