I love the Garmin Fenix series. Always on screen with 14days of battery life, notifications, and excellent exercise and health tracking, music storage, spotify support, etc. The battery life is achieved by not being glitzy like Apple watches, and using a "memory in pixel" display.
I'm now using a PineTime since a few months and quite like it. While it does not have that many features and is not the most stable one, it is very cheap and fully open source. The community is constantly working on the main OS and there are even a few alternative OS's to choose from.
You can get an okeyisch Android integration with GadgedBridge.