A lot of phones already have the capability to recieve broadcast band FM, the type and electrical length of the antenna matters a lot less when you're just receiving signals.
You do SDR on your phone? The last time I played with one of those dongles was like a decade ago and mostly I used it to check out NOAA satellite data and eavesdrop on air traffic control at the local airport.
I wonder how useful that would still be to keep tabs on the local pigs during the protests the next time they murder someone?