After launching with a heart rate monitor, the Apple Watch has over the past few years gained features such as GPS, a barometric sensor, electrocardiogram hardware, and fall detection. Now a Bloomberg report suggests Apple is planning to add another capability to the Watch in 2020: sleep tracking.

Thus far, no Apple Watch has promised more than a day of battery life, with Apple typically characterizing the guaranteed run time as 18 hours — enough to demand nighttime removal and recharging. Adding sleep tracking would imply that Apple intends to lengthen the device’s run time to more than a day, or that it is planning another way around its energy limitations. Given recent improvements in chip miniaturization┬áthat will enable processors to consume less power, the former scenario is more likely.

According to the report, Apple has been testing sleep tracking over a several-month period at “secret sites” near its headquarters, following its May 2017 acquisition of sleep tracking accessory maker Beddit. Based on the company’s typical hardware development cycles, successful testing now would result in the feature actually debuting in 2020 devices, rather than those intended for release this fall. Assuming Apple continues its current naming scheme, that would suggest integrated sleep tracking will arrive in the Apple Watch Series 6.

Sleep tracking and shorter battery life are on the short list of omissions that have prevented the Apple Watch from completely eclipsing less expensive rivals. Competing devices such as Fitbit wearables purport to measure the timing and quality of sleep based on a user’s movements during the night, sending the motion data to be viewed on a companion device. Apple-owned Beddit’s trackers are instead mounted within the bed itself, using Bluetooth to synchronize data to a phone.

To support Beddit and other sleep trackers, Apple’s iPhone app Health is already capable of receiving sleep tracking data, which it suggests can help a user “stay consistent” in going to sleep and waking up at the same time each day. It’s unclear whether Apple will use medical research and/or superior technology to improve upon the somewhat questionable results generated by earlier trackers or will merely mimic them in the Apple Watch.