How do I create a "pro" plugin that gets updated?

I have written a plugin. It will be called something like

ElephantPM Gantt Chart Lite

I will put this into the official WordPress Plugin directory.

I also want to make a chargeable version of this

ElephantPM Gantt Chart Pro

I would like to be like wpmudev and

* protect revenue with an API key
* provide automatic updates to "pro" customers.

What are my options? Which do you recommend?