iOS decides when background checks happen. A Shortcuts automation asks for one at a time you choose.
Ballast then checks every backup and sends its usual alerts if something changed. Background checks and alerts need the trial or the unlock.
It still runs on your phone. If the phone is off, or iOS holds the automation back, nothing happens. We haven't confirmed how it behaves on a phone that has stayed locked since a restart. For alerts that don't depend on your phone, see Alerts while your phone is asleep.