I recommend a modern iPad in Guided Access, dedicated, in usually a Living Room, and if you’re so inclined you might want to add a USB Lighting Adapter with a USB Ethernet adapter. You can also do that as a wallmount with say a SurfaceMount device. I prefer that path because it uses the latest A series CPU and thus provides the best video decoding. If you don’t use cameras or don’t use Remote Access or simply need to sync configs between two devices, you may need significantly less horsepower. An iPod Touch 6 might be suitable.
An Apple TV is the cheapest and very comparable option. It also has Ethernet built-in so it’s very simple to get great network performance, and medium video decoding performance (great with an Apple TV 4K).
This is discussed in the announcement as well: