https://www.cnet.com/news/apple-watch-series-5-rumors-price-fitness-battery-and-everything-else/

The Apple Watch would need better battery life for sleep tracking. Currently, it can last up to a day and a half before needing a recharge. The Apple Watch Series 5 could add a more efficient processor that can switch to a low-power mode at night... or, perhaps just increase the size of the battery. Reports of improved battery life are already out there. Qualcomm's new Wear OS chips last year were aiming at similar longer-life features, too.

EKG was a standout feature on the Apple Watch S4... what's next?