Facebook is probably doable, Skype I doubt.

The "add account" icon is currently just a link to the corresponding screen on you device. The purpose it to save you having to back out of the Gmail Widgets configuration screen to add another Gmail account. 

If you would like Facebook, Twitter, LinkedIn or other notifications, you would have to configure those services to send you emails to your Gmail account.

We are, however, looking at integrating other sources directly. Which one would you be most interested in?

Any luck with the updates I have released since then?

WIP

Done. You can get version 5.2 from Google Play now.