Pebble was a smart watch which was not tethered to a phone, talked to the cellular network directly, and had battery life problems, correct? Apple's smart watch was tethered to a phone, so it needed less power.
It's going to be interesting to see what happens when solid state batteries become available and increase how much energy you can store in a watch. They're high cost, but if you're powering a watch, not a car, probably affordable. That could make standalone watches more effective. Maybe eliminate the need to carry a phone all the time.
Pebble smart watches are tethered (to an android/ios device via bluetooth), do not talk to a cellular network, and have had an especially good battery life because of that and their low-power displays which are always on and visible with external light, only turning on the backlight when you are using it (e.g. hitting buttons or after giving the watch a little shake). afaik, every Pebble watch has had a significantly longer battery life than all of Apple's watches even though they're always displaying.
The newer Pebbles do have a better battery life, lasting multiple weeks maybe thanks of better battery tech.
I think most of the battery life improvement is the much more power-efficient SOCs available. The original Pebble used an STM32 processor and a TI Bluetooth chip, where nowadays having BLE integrated into the SOC is table stakes.
The opposite, Pebble is tethered to a phone, has Bluetooth but no cellular. Not even its own wifi connection, any data that a watch app needs is requested over bluetooth from the companion app on the phone, which fetches it from the internet.
Battery life was great, upwards of a week between charges, because connectivity features were very limited. It gets notifications, but you're not taking phone calls or checking email through it.
It's going to be interesting to see what happens when solid state batteries become available and increase how much energy you can store in a watch. They're high cost, but if you're powering a watch, not a car, probably affordable. That could make standalone watches more effective. Maybe eliminate the need to carry a phone all the time.