The official Watchy firmware is designed to put the esp32 into deep sleep and only wake to update the display, which being e-ink doesn't need any further power

The official Watchy firmware is designed to put the esp32 into deep sleep and only wake to update the display, which being e-ink doesn't need any further power to hold its position until the next update. In deep sleep no radios are on and the esp32 uses very small amounts of power. In my experience, I usually have to plug it into charge every ~10 days. As far as bluetooth on Watchy goes, it's more useful for OTA updates than anything else. When in this mode, Watchy's firmware can be sent as a .bin over bluetooth. This takes only a few minutes and then the ble radio is turned off. No real hit the battery. The other [quicker] way to flash the firmware is via usb, during which time the battery is charging. What I like about Watchy is that it requires no phone or apps, is running firmware I wrote and flashed, and occasionally calls my server for data if I need it.