Im still fiddling with my 3d printer to get it working after sitting on a shelf for most of a year because of a move so I can have a nice case for this but I was able to get this setup with these parts for ~$30 in parts not including the Pi and SD card. Setup was a breeze and there is some mouse lag but if you turn on the mouse dot option in TigerVNC then its not noticeable at all.
I use it mostly for remote access to my Windows environment that I can't run as a VM. I would like to get a cell radio addon for true out of band remote access with one of the IOT type cell plans but I need to do more research on that.
It's good for critical systems that you might need to reboot and do things like see the BIOS (which you can't see if you're using a normal VNC-type remote access solution). It's probably not necessary for most setups, but it can be very useful in certain situations. I made one myself, then literally never used it, and I'm now using that Pi in a different project.
I thought about setting one up for my main server because every time the power went out I'd have to reconfigure the bios for boot order, virtualization, and a few other settings.
I've since added a UPS to the mix but ultimately the fix was replacing the cmos battery lol. Had I put one of these together it would be entirely unused these days.
It's a neat concept and if you need remote bios access it's great, but people usually overestimate how useful that really is.