You can create a custom Scheduled Action that periodically checks the container filesystem for the backup files and compares the date from one of them to a date you have stored in a System Parameter, then take action when you detect a difference.

The backup file is stored in

/home/odoo/backup.daily

Look for a folder, a *.json file and a gzippped *.sql file with _daily as the last 6 characters. ​