The computer is the easy part — any 10-year-old Android phone would do the compute part, and the networking part, and the screen part; and would be easier to pr

The computer is the easy part — any 10-year-old Android phone would do the compute part, and the networking part, and the screen part; and would be easier to program; and would cost less than pretty much any SBC kit. The hard part (at a DIY level) is, honestly, the physical buttons and knob — wired as an input device to the compute without hogging the device's (likely only) port — and with good industrial design (no gross 3D-printed textures that easily get dirty from being touched a lot; no deep wraparound plastic bezel that prevents you from touching the corners of the display; dynamic-function side buttons thin enough to allow the screen to show the labels for them; etc.)