I've used the XPages Social Enabler which comes with great functionality to handle the authentication including SSO and functionality to invoke REST services easily and parse XML. I also used the documentation of the Connections REST services. If I have time I document later more how I've done it. For now you can read the source code on OpenNTF. I want to thank my colleague Yun Zhi Lin whose code I used as starting point.
On the XSnippet page there is a new icon now to share on Connections.