Hi, looks like there are quite a lot of smartwatches based on JL701N BR28 however there is no public SDK on their github.
Only the bootloader project supports it.

Do you have more info about that one? Maybe you possibly have access to the SDK for the JL701N watch devboard?
https://www.aliexpress.us/item/1005006308125435.html

The DaFit mobile application has ~900 watches based on JL701N in its database. One example is Zeblaze GTS 3 https://zeblaze.info/gts3.html with firmware update available here
https://qcdn.moyoung.com//files/DHdJG80gtjagB3ezS9WoHyN81jdeddtN.ufw
Currently it is $8-$15 watch on aliexpress https://www.aliexpress.us/item/3256806229302356.html

here is some random info I found
https://inf.news/en/digital/2194c6123b2fce2876a86fa4e91d1fdb.html
https://blog.csdn.net/weixin_44893015/article/details/126847330

Do you know why they omitted 701N chips at https://gitee.com/Jieli-Tech ?

Was thinking about custom firmware for those Dafit watches like we currently have for nrf52832/40 DaFit watches. nrf52 is OK but sadly smartwatch manufacturers moved away from nrf5x platform.

One crucial question is whether the firmware is somehow signed/encrypted or custom FW via OTA is possible without having the signing key, can you guess from moyoung download above whether there is chance to modify and reupload that file? I see you have some ghidra stuff, maybe you also know how to unpack ufw file?

EDIT: forgot some links
official one for 7012 with some specs https://www.zh-jieli.com/product/showproduct.php?id=33
here some random documentation using 701N as example https://doc.zh-jieli.com/Tools/zh-cn/mass_prod_tools/private_data_auth/tools_modification_section.html (despite no other SDK or documentation published for 701N)
commit adding JL701N to bootloader Jieli-Tech/fw-Bootloader@40dc675 plus some dual bank update Jieli-Tech/fw-Bootloader@8efd17e