@ReimuNotMoe@blind_via For what it’s worth, a 0.6mm and 1.6mm ENIG PCB are the same price from JLC in QTY 30 ($22.50 for 25x27mm)
Also there is a pretty popular hobbyist project using this exact method but with microusb instead: https://t.co/BPYpW8VcaN
@Willrandship So I went in another direction, get a physical connection on the watch. I use the buttons as ground and the back of the watch for data. This connection allows me to update the firmware and transfer data to/from the watch.