This is an open-source extension for Google's social network, Hangouts. It allows you to receive notifications for specific tabs in Hangouts, so you can be notified when a particular conversation starts or ends.

Hangouts Notifications is an open-source project, which means that it is not limited by any particular company, and you can download the source code to see what's inside it. It can also be used by other companies, which means that there is no restriction on how many people you can be notified about.

It supports multiple hangouts instances at the same time (for example if you're using both Gmail and Inbox).