These are the files needed for the DaFlasher app, Playstore: https://play.google.com/store/apps/details?id=com.atcnetz.paatc.patc
After flashing you will end with an Nordic DFU Bootloader where you can flash your own Firmware to The Watch. Like via Arduino etc.
I recomment to have one opened watch to develope new Firmware and when it is tested upload it to the closed Watch
Here you have the 3 Files you can see me using in this video:
(click on the image)
https://www.youtube.com/watch?v=gUVEz-pxhgg
This gets you started, flash this file first when you are on the Stock DaFit Firmware, this will install an Custom Bootloader i made using the Installed SoftDevice5.0.1 Here is a list of all the Compatible watches that can be flashed with this "Hack" https://gist.github.com/atc1441/d0a3c1f5ee69ab901bccba4eb47a6e4e
This installs the SoftDevice version 2.0.1 and an Bootloader for SD2.0.1
This is just a demo Made for the P8 Smartwatch to show the hardware is working, it will also run on other Watches but maybe they have different pinout for aditional Hardware like the Push Button.