When the pandemic hit, Apple and Google were keen to have a unified contact-tracing solution built right into iOS and Android. That helps, because the lighter it is, the more likely it is to be used.
With a view to the invasion of Ukraine, Russia is also conducting airstrikes, now increasingly targeting civilian places where people live. Anyone who follows certain media on Twitter and Co. knows the alarm for air raids.
XDA found a hint that Google could integrate a warning directly into the OS. Android could then issue a warning, even if you don’t have an app installed on your smartphone.
As with contact tracing, an update would not be necessary. Google will do this again via Google Play Services. You now have many options without having to distribute an Android update.
Incidentally, so far there are only indications that Google is working on it, you have not yet confirmed this yourself. Let’s hope that this new feature might save lives and will never really be relevant to us.