I helped design and have manufactured a smartwatch style health tracker as part of a research project: https://amulet-project.org/ https://amulet-project.org/

I helped design and have manufactured a smartwatch style health tracker as part of a research project: https://amulet-project.org/ https://amulet-project.org/ It cost somewhere around $200-$250 per watch in a quantity of 150 five years ago to have them made and we did final assembly (putting the PCB into the 3D printed case) ourselves, as well as testing. The MCU was an MSP430, there were a variety of sensors, microSD card, USB charging, an e-ink display, a Bluetooth LE radio that talked to a smartphone and external wireless sensors, and touch sensitive buttons/slider. This is the company that built them for us, I'd recommend them: https://www.emeraldems.com/dataed/ https://www.emeraldems.com/dataed/ They can help with design also, though I've only used them for manufacturing. The software is available here: https://github.com/AmuletGroup/amulet-project https://github.com/AmuletGroup/amulet-project Note that because the radio chip is often revamped the one we used is now obsolete, which also obsoletes the radio firmware. Some of the other parts have also become obsolete (chips go obsolete fast!) That said I'd recommend hacking an existing smartwatch instead, they are really cheap and it is easy: https://hackaday.com/2021/07/08/reverse-engineering-a-very-cheap-fitness-band/ https://hackaday.com/2021/07/08/reverse-engineering-a-very-c... https://hackaday.io/project/144350-hacking-wearables-for-mental-health-and-more https://hackaday.io/project/144350-hacking-wearables-for-men... https://hackaday.com/2018/05/04/hacked-fitness-trackers-aim-to-improve-mental-and-physical-health/ https://hackaday.com/2018/05/04/hacked-fitness-trackers-aim-... https://hackaday.com/2018/05/29/hacking-a-fitness-tracker/ https://hackaday.com/2018/05/29/hacking-a-fitness-tracker/ Designing your own system and board and making it reliable requires a lot of special knowledge. For example, did you remember to add anti-static protection diodes to all external electrical I/O? Does your battery management keep the battery from discharging to too low a point? If you have more than one MCU how to you synchronize them? How do you keep accurate wall clock time/date? How do you get data on/off the device? Where should you put test points on the PCB? What connectors are reliable? Does your Li-Poly battery need a protection circuit? Do you need it to be waterproof? So designing something close to a product is not easy. It took us years and several very different prototypes and the end product was still a prototype (no waterproofing for example and not impact resistant). If you're just doing this for fun and are ok with something less polished or are interested in building a prototype, then by all means try designing your own, it is not too hard to get a working PCB and design a 3D printed case for it. You can find several examples of people making their own smartwatches on HackADay.com which might helpful.