Is there a smart watch (bracelet) with open firmware?

Question

Do it yourself

Is there a smart watch (bracelet) with open firmware? To add your own functionality, remove the unnecessary?
Or a whale, or a DIY project that has normal dimensions and a price not the size of an airplane wing?

Answer 1

https://www.chooseblocks.com/
https://asteroidos.org/
oswatch.org
But this is not exactly what you want.

Answer 2

No, DIY is not possible in principle. Do-it-yourself projects are always larger in size due to convenient connectors and extra outputs during the operation of the finished device. Even if you find a DIY clock, it will be wall-sized, not wrist-sized.
It is practically impossible to assemble wearable equipment at home, you need at least a hair dryer to solder the chip to the board. Then it's better to take the finished device and unsolder the same chip and flash everything you need into it.

Answer 3

Or a whale, or a DIY project that has normal dimensions and a price not the size of an airplane wing?

Conventional consumer devices are so compact and how cheap just because of the huge millions of copies
, by definition, orders of magnitude fewer people are engaged in DIY. Therefore, with the same features, it will be more expensive and more voluminous.
There are very rare exceptions:
www.ti.com/tool/EZ430-CHRONOS
Additional external sensors can still be purchased separately.
Sharpened specifically for DIY.
This is how Texas Instruments introduces its MSP430 microcontroller.
But even here it is not without limitations - the firmware is not a full-fledged OS like Tizen or Android, where you can run any application, therefore, there is no full-fledged Bluetooth stack.
There is a real-time OS in which application software integrates with the OS.
There is a wireless connection. But communication standards from the world of IoT, and not with the more familiar BT / Wi-Fi.
On the plus side, it consumes very little electricity.
The batteries last for a very long time (unless, of course, it is programmed correctly so that the extra functionality goes to sleep when it is not needed)
The MSP430 microcontroller is rather weak, but it is great at saving electricity.
It can live from a watch battery for years , while regularly transmitting information over the radio channel (which in itself consumes a lot of electricity from faster devices)
======================= ============
At the other extreme is a watch with Android on board. They consume a lot of electricity, at best, for several days of battery life, but the functionality is richer.
Applications are written there. You can't change the firmware itself.

Answer 4

This topic is also interesting. I started drawing a board for a 1.3 "240 * 240 display on st7789, as a controller, the ttgo pico d4 (esp32) module. Now the microcontroller itself, rtc, mpu, barometer fit on the board. Passive elements of size 1206 can be reduced. But I have absolutely I have no experience in creating such devices and only meager experience in programming arduino, so I'm unlikely to finish it.