For years I used "StartServiceAt / StartServiceAtExact" to wake up the device every minute and update the status of the app. and check if they were set alarms or reminders for that time, then I brought back to sleep the device, all this very little affected the battery life.
With the latest Android versions are forced to use "StartServiceAtExactWhileIdle", I hope will you implement as soon as possible in B4A ...
which still to run on all devices you need the application to be excluded from battery optimization (not counting the various alerts that are sent to the user by the operating system ...). as you solve?
greetings to all