With Real Mouse you will be able to navigate through main and secondary (external) displays with a simulated touchpad. Due to Android limitations you won't have "smooth" cursor on the main display while on the secondary displays you do. Image you launch an app on an external monitor or any of the secondary displays in the developer options menu you will be able to use the virtual trackpad to navigate through the apps with a breeze and it works just like a real mouse (it is as the app talks to the /dev/uinput kernel module directly)!