HP is set to release a new all-in-one (AIO) for 2019: a modular one. The Mini-in-One 24 Display looks like just another 1080p monitor. However, it has an enclosure at the back into which certain HP Mini desktops can be slotted. The Display can then use this PC's I/O as its own.
https://www.notebookcheck.net/HP-debuts-the-world-s-most-secure-modular-AIO.422357.0.html