The SharePoint Saturday Belgium 2016 presentation by Alexander Meijers focuses on extending Office 365 to cross-platform applications using Xamarin and demonstrates implementation techniques, including Active Directory Authentication Library (ADAL) for user authentication and querying user profile data via SharePoint's REST API. Key topics include code-sharing strategies, project setup requirements, and using Xamarin.Forms for a unified user interface across platforms. The session emphasizes the advantages of using the Xamarin platform for cross-platform app development and highlights necessary tools and techniques for successful implementation.