I don't think that's a feature a whole lot of phones will every support.
From what little I know about pirate radio most "criminals" involved attract attention because their low-teck equipment causes their signals to wander into the Airband.
The highest FM frequency that can be broadcast on is 107.9. That's in MegaHertz. After that 108 - ~140 is the Airband. It's specifically designed for civil aviation.
"PLEASE TURN OFF ALL ELECTRONIC DEVICES" is especially important if your device has an FM transmitter. If everyones phone had one they really could cause serious problems on commercial flights.
Pilots really do need cross wind speeds etc when they're trying to navigate a safe landing not third-eye blind wandering into their band as you steam from your phone to your cordless FM headphones.
It's a nice feature but I'd rather it stay a separate device rather than a built in bit of hardware that accidentally gets called up when you're casually messing with your smartphone on a plane.