It might be a good feature for the elderly as long as it’s local and optionally enabled (especially if it can be enabled only for unknown callers).

Yes, I understand you would never really know if it’s not always enabled. But then again, you currently don’t know if anything similar isn’t already enabled.

For other users, again potentially useful if it’s opt in. However, many people (myself included) simply don’t answer the phone anymore unless it’s a caller we already know. I use Google’s call screening feature for any other caller not in my contact list already, and I would estimate about 1 in 20 or 5% of such calls I receive aren’t spam (marketing or fraud). Of those non-spam calls, the majority are appointment reminders I don’t need.

So would I turn this feature on? No, I don’t have a need. Could it be beneficial for the elderly? Yes, but probably not implemented in a way where it would actually be effective.