Walkie-talkie apps on smartphones, like Zello, still require working Internet access. They don't work without cell or wifi service and internet access. Zello keeps reminding people, it REQUIRES internet access; but people don't get it.
Only about 5% of households have a NOAA/Weather radio with battery backup (slightly higher in tornado alley).
The Serval mesh project is specifically meant to address the situation of no Internet or cell access. Caveat: it hasn’t been updated recently and the Google app store no longer has it. It is still available via F-Droid. It looks like it may be useful if one has a working network that is not connected to the Internet (or has a very poor connection).