Genki Studio is described as 'Software that turns your iPad into a portable monitor and video capture device. It connects to a Genki ShadowCast or any USB UVC device, with features like external monitor support, Apple Pencil markup, and multitasking' and is an app. There are more than 10 alternatives to Genki Studio for a variety of platforms, including iPad, Mac, iPhone, Windows and Android apps. The best Genki Studio alternative is Side Screen, which is both free and Open Source. Other great apps like Genki Studio are Duet Display, superDisplay, Orion HDMI Monitor and Splashtop Wired XDisplay.
Orion is a great alternative, although unlike Genki Studio, the latter has support for making annotations while displaying with an Apple pencil