He didn't really mean it.
But I made him one anyway:
Arduino Nano and NeoPixels with capacitive touch sensor.
It's not really a clock as such, more a timer. You twiddle the knob to zero (all white) and touch the top of the box, at which point it counts up in five second increments. You set the time with the knob, touch the top of the box and it counts down to zero. You twiddle the knob while it's timing and everything stops.
Good thing he didn't ask me to make heavy ordinance. Can't help myself, can I?