The Kaleido concept mini PC is not really that small, but it sure packs everything you need from a computer. First of all, you do not need a display, since the elongated prism-shaped device integrates a projector, plus it also comes with a foldable keyboard and a sound bar.
https://www.notebookcheck.net/No-display-required-Kaleido-is-a-mini-PC-concept-with-foldable-keyboard-and-integrated-projector.453106.0.html