This is really a silly idea, for the several reasons already stated.
If you want to be informed about weather, nothing beats live bodies, radio, and listeners when combined.
Next step would be auto-vibrate and ring on weather alerts.
I don't want my phone to alert me that a tornado is aimed at point 20 miles south of me.
We have enough data now to make such a feature useful, we could actually feed GPS data from a twister's position
to cell providers and then CALL people within a "cone" of possible danger.
Like the NOAA radio's alert feature, which drove my dad nuts, this feature needs to be something that can be acknowledged
and voluntarily silenced if desired for a user determined time.
Otherwise, you might just as well broadcast such warnings in spark gap damped oscillations on 500 khz, too.
I certainly won't be listening to FM on phone, I have real radios everywhere I go, except when I'm working
out in the pressroom, where it's too loud to not wear earplugs, then earbuds won't work, and unsafe to not hear
everything going on, and the RF noise in a pressroom is about the worst that can be imagined.
There are at least two radios on at all times, one in QC, another on a press. Fixed position radios can usually get enough
signal 25 miles out from the city but with all the noise, antenna placement is critical.
Walking around, you can't really listen to a radio signal in this place.
I would always want to plug the phone into some kind of amplifier, but then why not a real radio anyway?