As as you probably noticed when Exchange 2013 SP1 was released a couple of weeks ago, we now support OAuth based Exchange hybrids. If not check out this TechNet page.
Well, now we have also released documentation on how to use OAuth to support eDiscovery in an Exchange hybrid scenario.
Moreover, Exchange Server 2013 allows other applications to use OAuth to authenticate to Exchange. This page shows you how to configure this for Lync 2013 and SharePoint 2013.
See where this is heading? :)