Mobile Reports are dashboards that will run on most modern mobile devices as well as within the web portal. They are supported on IOS 9 and later, Android 4.4 or better, and Windows 10. To run Mobile Reports on these devices, the mobile Power BI application must be installed.
At first glance, they are simple to create. There is a new tool to use, the SQL Server Mobile Report Publisher. The tool will look familiar to you if you have worked with Datazen in the past. Microsoft purchased Datazen in 2015.
This is the first major Reporting Services update since 2008 (unless you consider sparkline support in R2 a major update), and could be a good business justification for upgrading to SQL Server 2016.