As of right now, Ubuntu Linux still ships Empathy as its default IM client. I won’t go into how bad that thing is, but at the very least it doesn’t even support proxies, so Pidgin is the only way to get things working properly. Pidgin on Unity already supports integration with the indicator-message in the top-right corner, but there’s one important feature it hasn’t integrated: showing the unread message count on the dock icon, the way Empathy does. In fact, someone made support for this a long time ago, it’s just that it’s only recently gotten on track. If you’re on Ubuntu 14.10 or later, you’ll find this plugin in your Pidgin install.