this is just a factibility analysis.
its a while that i think about doing a custom watch, like picking up the case from a standard analogic watch and fitting the inside with a custom board.
for now i was thinking about using a arduino and a few touch buttons in order to do everything, but now i was watching the esp32 and i saw that it has both an integrated rtc and 10 touch pins, this means a lower footprint and a lower current consumption.
my main concers would be about the BLE signal getting through the case, the antenna design and also the touch buttons sensitivity (there would be 4 raised pad pressing against the watch glass).
4 layers pcb are cheap (50x50 10pcs @1.25€ each) so i would give them a shot, but it would be a 38-40mm circular pcb, and thanks to the small dimension im not sure i can leave the antenna without any trace running over/below it.
any consideration? also, keep in mind that i have just a ds1054 as my main tool (for the antenna tuning (?)) and i have never worked with antennas design