VeriShow is the world's first multimedia platform for delivering live help and real-time sales support to website visitors. The Joomla extension enables you to interact with site visitors in real time using live chat, voice and video and access a host of collaborative tools, such as document, image and product-video sharing, a second-camera input and many others. You and your visitors can annotate those in real-time, for example to point out a feature on a product document or image.

Installation instructions: http://www.verishow.com/verishowforjoomla.jsf