It is pretty simple to do this in the app. On the hail announcement window, just above the payment mode that the rider has set, there is an overflow menu( Three dots arranged vertically) if the app is runing on the foreground, and a magnifying glass with the label 'Details' if it is running in the background. Tap either of the two to reveal a drop down menu and select 'Show Trip Destination' to see rider's destination.