HTTPS SSH
This is an extension for Google Chrome that makes an LED of your notebook running Linux, blink while...

Gmail
* you have unread emails in your inbox
* you got a message via Hangouts
* you got a message via Google Talk

Google Plus
* you have unread notifications
* you got a message via Hangouts

IRCCloud
* your nick was mentionen in a chat
* you got a private message

Pinned tabs
* the title has changed (similar to the built-in behavior in Chrome of flashing pinned tabs)