The fact that phones haven't been able to to this easily/natively/what have you is wild. Similarly, the fact that you can't use old tablets as external monitors without, in my experience of quite a few, significantly buggy software that's got significant lag in the best of times, is pretty wild. Sure, the technical hurdles aren't small, but damn.
I've got a reasonably high end newish tablet (Galaxy S7+) that I can use miracast to use wirelessly as an extra PC monitor. It works quite well... if I'm near to a high quality new router. But can I just plug the tablet in and use it as a monitor with my laptop? Not remotely well.
It's been a year or two, maybe I should check for new software again.
You can plug an iPad to a MacBook via usb c and use it as an external monitor and it works really well in my experience. Kinda makes me wonder if there isn't a patent somewhere preventing it from wider use.
Ive been using an app called SuperDisplay. It allows to connect an android device through cable. It only requires to install their software on the PC first. It's a paid app with 3-day trial, so you can test how it works.
I hate that this is only just now coming in Android 14. I have old phones I would love to be able to set up as webcams for 3D print monitoring, but of course they haven't been updated in years and will never get this feature.
This is already possible - there are apps that will let you use any android phone as an IP camera, which you can then view from any other computer or phone on the same WiFi/network
The real blocker here is the kernel must be compiled with UVC support, which is only enabled by default on many devices since Android 12. Custom ROM could enable this on older android devices, but I doubt it'll happen because custom ROM usually reuse the device's kernel instead of compiling their own version of kernel.
The one I paid for (iVCam) works with OBS and Twitch, can do full 4K@60fps and stuff. I had never seen a free one that worked with my other apps, allowed even just full HD, and didn't have a watermark. I definitely would have preferred something totally free tho.
IP Camera looks like it only works with VLC or a browser according to its description. The built in support for it on Android might not actually do what I want either... 🤔