Yeah they're ready-to-go touchscreen interfaces/displays that can be implemented in tons of ways. I've been thinking about setting up my old Note 4 as a touch screen interface for my 3D printer, and old tablets as wall mounted interfaces for Home Assistant, which are just two possibilities.
Unfortunately the Note won't run off USB power alone so I'll have to hack together a solution that tricks it into thinking the phone is being charged with a battery in it.
I was poking fun at the seeming desire for a physically tethered phone as to power a device without a battery, it would need to be plugged in.
But also, you may have missed the likes of ELKeyko Wireless Phone 2021 The 4G LTE Android 10 Fixed Wireless/Cordless Desktop Phone with VoLTE, WIFI,BT and WIFI HOTSPOT Smart Phone Cordless landline https://amzn.eu/d/ffotKoV