As seen on Hacker News, the PubNub Channel Presence Introduction talks about Presence Capabilities and the reason its for existence. Take note of this awesome new feature made available by the worlds Best and First Global Presence Infrastructure. Nothing like this has existed at this level of scale. The Real-time Web for Mobile Apps and Web Apps is notably a powerful advent following HTML5 WebSockets, WebRTC and more. Now with PubNub you can create group or one-to-one chat apps on all platforms easily without having to consider technologies or transports as discussed in the Are HTML5 WebSockets the Panacea for Real-Time Data Push article - blog.pubnub.com/are-html5-websockets-the-panacea-for-real-time-data-push/
With PubNub Channel Presence, you can provide Live Real-time stream of information based on the availability of users on your channels. You can update timelines to provide a peek into the past while providing up to the nanosecond activity at this very moment in time.