Use linked arduino shield on RPi, just need some logic level translator and new software.
All Radiocom is done on shield (by undefined chip), arduino only control.
Radio Spectrum are controlled all countries, some have a very rigid law about non authorized radio emissions (even listening).
On most countries have a some bands, called ISM (Industrial, Scientific and Medic), frequencies that can be used without any previous permission, but at very low power (<100mW). WiFi, bluetooth, and other consumer wireless devices use these bands, and linked arduino shield.
In theory, with a extra $10 hardwares (to receiver part/audio in) is possible to build a NFM transceiver using only RPi. And lots of programing.
Due some early controversy about, I can not provide more details.