Another interesting device in this arena, Pine Time: https://www.pine64.org/pinetime/
Of note, PineTime is water proof. Which at least for myself is a big deal.
The breakdown chart on the first link above comparing with other watches is interesting. Watchy seems like it can do a lot more. But I do wonder about battery life.
I got mine a week or two back so I haven't actually had time to run the battery right down (spent too much time plugged into my computer programming and debugging), but the software I've put together so far the battery life seems great.
Over 24 hours, the voltage value I've been displaying (rounded to the nearest tenth of a volt) went from 4.2V to 4.1V. So even under the most unfavourable rounding that's 0.1V over 24h, or still about 95% battery charge. That would be almost 20 days doing some basic processing, screen updating, etc every minute.
I'd agree about the waterproofing, however. Wearing it for a few days and knowing not only that it's not waterproof but exactly how _un_waterproof it is, it's made me a lot more conscientious about handwashing and day-to-day activities.
How're you calculating that? Voltage of (what I assume is) a lithium ion cell is a pretty poor way to measure state of charge - the discharge curve maintains voltage pretty well until 80% capacity before falling off precipitously.
You certainly aren't going to get any work out of the cell below 3V or so without risking permanent damage.
Just googled "lithium polymer discharge curve" and averaged between a few results. Generally saw an inverted S shape where the first few tenths of a volt should be shed pretty quickly before stabilizing for a while, then dropping precipitously as it neared dead (~3V).
I don't know who is wearing a bare PCB on their wrist. Especially since the battery (lipo pack) is stuck on the back, so you've got a bare lipo battery sitting against your skin all day.