In order to keep a device's battery working well over many years, I think it would be a cool idea to implement a feature where one could have their device charge up to ~85% or so overnight and then stop if an alarm is set. Then as the wake up time approaches (if the user has the feature enabled) the device tops the battery off just before the alarm goes off intelligently.
Doing this would reduce the stress on the device's battery cell and keep the maximum capacity/run time for a longer period before the battery would degrade! This would be great for those who keep their phones for many years and don't want to have to get their battery replaced down the road. Also, it would increase the long term resale value of devices which would likely attract customers afraid of their device not being worth much after years of use!