A new tutorial is completed: How to write a High Trust-App for SharePoint for non C# languages. The tutorial highlights how to access the API with the Bearer-Auth-Token.
Please note: Node.js is not strictly required for this kind of technology. But it shows the basic approach, you can reimplement it in any other language like PHP, Python, Java, Perl, etc.
Because I did not find any article about this topic that has all the details, here are some keywords for crawlers:
SharePoint 2013, App, HighTrust, s2s, Server2Server, OAuth 2.0, ACS not available, Azure, Microsoft Cloud, SharePoint Store